ALTIUS Chem 1

History of Radioactive Decay

Becquerel worked with uranium compounds and placed on film that was wrapped in dark paper after some time the film darkened indicating energy had been transferred Becquerel first assumed it was the sun giving energy to the film, but when he put the Uranium in an enclosed spot away from the sun the paper was darkened as before Becquerel concluded that the Uranium must be emitting some sort of high energy thus discovering radioactivity. He later demonstrated how the radioation energy was like x rays, but unlike x rays could be deflected by a magnetic field awarded Nobel Prize in 1903 then worked with Curie's in discovering polonium and radium Ernest Rutherford discovered alpha, beta, and gamma radiation in 1899

Reactions

Combustion Synthesis (Combination) Decomposition Displacement https://chemfiesta.org/2015/09/08/the-six-types-of-reaction/

History of atomic structure

Greeks divide atom until indivisible Dalton- atomic theory that all matter of spheres called atoms that combine to form compounds Thomson- atoms are composed of subatomic particles as they could be split with charged voltage on gas (discovered electron has less mass then proton) but came up with pudding model where charges are equally distributed and cancel out (was also wrong about size of particles) Rutherford- nucleus in center were mass was (completely bounced back alpha waves which was unexpected) positive charge in center while electrons were in a cloud around why didn't the e- collapse into the nucleus Bohr- atom has fixed energy levels at fixed distances

Orbits and Orbitals are different: Heisenberg Uncertainty Principle

Heisenberg Uncertainty Principle: can't know with certainty both where an electron is (position) and where it is going (momentum) because an electron is both a particle and a wave so since uncertainty can't have specified orbits of position and momentum so when 3D mapping we plot all the locations where an electron has been and start to see a shape appear that indicates the probability of finding an e- there (THIS IS AN ORBITAL) and e- can be elsewhere outside orbital http://www.chemguide.co.uk/atoms/properties/atomorbs.html

Polyatomic Ions

Hydroxide = OH -1 Nitrate = NO3 -1 Nitrite = NO2 -1 Chlorate = ClO3 -1 Chlorite = ClO2 -1 Hypochlorite = ClO -1 Perchlorate = ClO4 -1 Carbonate = CO3 -2 Bicarbonate = HCO3 -1 Ammonium = NH4 +1 Sulfate = SO4-2 Phosphate = PO4+3 Manganite = MnO -1 Permanganate = MnO4 -1 Cyanide = CN -1 -ATE = 3 oxygens except in sulfate SO4 or Phosphate PO4 Carbonate and Sulfate and their family are -2 Nitrate and Chlorate are -1 Phosphate is -3 Ammonium is only polyatomic with +1 https://www.youtube.com/watch?v=MTEgkWc2-nU

Mole-to-Mole Conversion

Mole serve as a hub that can convert to several different properties PV=nRT (6.022*10^23 /mol) molecules, ions, atoms density: g/ml (molar mass g/mol) moles of another molecule: mole ratio of balanced equation Molarity: mol/L Grams: molar mass (g/mol)

Zero-Order, First-Order, and Second-Order

Rate=k[A]^m THE UNITS OF K CHANGE FOR EACH ORDER AND UNITS OF K DETERMINE WHICH GRAPH IS LINEAR RATE IS ALWAYS M/s, so k are units that produce final M/s ZERO ORDER m=0 (zero order) rate = k k units are M/s (concentration over time) [A]/t = k k is constant so rate is constant meaning change in concentration is constant (straight line slope ZERO ORDER MEANS DOUBLE OR TRIPLE CONCENTRATION= NO CHANGE IN RATE [A] vs. time is linear and when linear slope tells us rate constant: k FIRST ORDER m=1 (first order) rate = k[A] k units are 1/s so that rate = M/s ln[A] over time = k rate gets smaller as [A] gets smaller so see graph with initial steep slope and gradual curve to a flat line where low[A] means low rate FIRST ORDER MEANS DOUBLE CONCENTRATION=DOUBLE RATE [A] vs. time is curved so can't find -k but ln[A] vs. time is linear so we can find slope = -k SECOND ORDER (1/[A] is linear) k = 1/([A]t) so graph is 1/[A] m=2 (second order) rate = k[A]^2 k units are 1/Ms or (1/[A] over time) graph shape is similar but curve is sharper since change is more dramatic [A]^2 compared to [A] [A] vs. time is very curved so can't find k ln[A] is still curved but less so 1/[A] is linear (REMEMBER ALL RATES ARE DETERMINED EXPERIMENTALLY, THE MOLE RATIOS DON'T INDICATE HOW FAST OR SLOW WHY? BECAUSE THERE MAY BE MORE THAN ONE STEP TO GET FROM REACTANTS TO PRODUCTS If only a single elementary step then rate law WOULD be determined by mole ratios, but if more than one step complicates things making it important to determine experimentally. but how can you tell if reaction only has one step (MUST BE TOLD BY PASSAGE, the balanced equation only gives starting and final doesn't mention any intermediates) again unlikely to be told because they may want to see if know difference between equilibrium and rate https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Experimental_Methods/Using_Graphs_to_Determine_Integrated_Rate_Laws

Displacement

SINGLE: A+BC->B+AC common as a redox reation Mg + 2HCl -> H2 + MgCl2 Ca + 2H2O -> Ca(OH)2 +H2 DOUBLE: AB+BC->CB+AD when cations of two compounds switch places HCl + AgNO2 -> AgCl + HNO2 in a solution, a precipitation is a double replacement reaction when previous soluble aqueous cations and anions combine to form insoluble solid CaCO3 (aq) + H2SO4 (aq) -> CaSO4 (s) + H2O (l) + CO2 (g)

Half Life Problems

The half-life of a substance (t1/2) is the amount of time required for exactly one-half of the mass of that substance to disappear due to radioactive decay. 3 variables: HALF-LIFE time where 1/2 mass remains, TIME that has passed, and GRAMS amount of substance do this conceptually in head. do not rely on a formula. one problem may give initial and final grams and give time that has passed. determine how many half lifes have occurred to go from initial to final and take time passed/total half lives to get time per half life which is the half life ALWAYS TAKE NOTES WHEN COUNTING HALF LIVES write every 1/2 that has occurred as well as the start and final amounts and time passed 1 half life = 1/2 2 half life = 1/4 3 half life = 1/8 4 half life = 1/16 and estimate estimate estimate when need to http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/halfli.html https://www.chemteam.info/Radioactivity/Radioactivity-Half-Life-probs1-10.html https://www.khanacademy.org/science/chemistry/chem-kinetics/copy-of-kinetics/v/half-life

Combustion

When Carbon and Hydrogen react with Oxygen to make water vapor carbon dioxide and heat C6H12 + 9O2 -> 6CO2 + 6H2O

Understanding Keq

X+Y-> Z rate of forward= Kf [X][Y] (depends on reactants) rate of backward = Kb [Z] (depends on reactants) Kf and Kb are rate constants (they are different) equilibrium is when forward rate=backward rate Kf [X][Y] = Kb [Z] Kf/Kb= [X][Y]/[Z] Keq= [X][Y]/[Z] so Keq is simply rate constant ratio, and because constants remain constant, so too does Keq, Keq DOESN'T DEPEND ON STARTING CONCENTRATIONS, the concentrations will balance according to the constant (not the other way around) Factors that affect Keq: identity of reactants and products (not how much reactants or initial products, HOWEVER removing product is a thermodynamic action) Temp Stoichiometry of equilibrium reaction

if rate law is: rate = k[Br-][BrO3-][H+]^2 what happens to rate when: [BrO3-] is doubled? pH is increased by 1 unit? solution is diluted to twice volume, while pH is constant?

[BrO3-] is first order meaning doubling concentration doubles rate (1:1) pH units are in a factor of 10 meaning change from 6-7pH or 3-4pH is a difference of 10x H+ H+ is second order meaning changing reactant by factor 10, means changing rate by factor 10^2=100 if volume is increased but moles kept same (remember PV=nRT P= n/V * RT increase volume by factor 2 lowers the concentration for each by factor 2 so 1/2 [Br] and 1/2 [BrO3-] both are first order so rate is lowered 1/4

Catalysts

any substance that increases reaction rate without getting consumed in process (same mass before and after reaction) (can change in middle but returns to original at end) (transition metals make good catalysts because the can easily revert oxidation states shape determines function so specific shape determines only specific molecules can bind and benefit by orientation arrangement from catalysts (enzymes) pharmacutical drugs work by mimicking the shape and size of reactants blocking active sites on enzymes (called inhibitors) alternatively helps by weakening the bonds of reactants and forming temporary weak bonds to catalyst that can further react to form product (understand that mechanisms for catalysts vary widely which is why definition is simply that catalysts are not used up and speed reaction) a bad catalyst therefore is one that doesn't form strong enough interaction with reactants or too strong and never lets reactants go remember collision theory and Maxwell Boltzmann distribution of energy of molecular energies in gas not just collisions that cause reactions, it is the energy they have that must overcome the Ea to react (otherwise they just bounce off like an light on an electron that doesn't meet the energy requirement to send e- to higher orbital) ALSO KNOW that particles can adjust their energies getting in collisions that increase or decrease energy so a low moving particle in one second could get the high energy and react and likewise a high energy molecule could lose energy, what is measured is the AVG energy CATALYSTS LOWER ACTIVATION ENERGY enabling a higher proportion of molecules to react what's also important is understanding that catalysts provide an alternative route for reaction with lower activation energy (meaning some molecules may still react on their own at the original activation energy (it is not technically true that catalysts lower activation energy) climb over a mountain or take a tunnel through mountain (the tunnel doesn't shrink the mountain) and when catalysts are too maximized, the excess reactants have no choice but to take the original higher activation energy to react CATALYSTS DON'T APPEAR AS REACTANTS OR PRODUCTS BECAUSE CATALYSTS DON'T CHANGE http://www.chemguide.co.uk/physical/basicrates/catalyst.html http://ch302.cm.utexas.edu/kinetics/catalysts/catalysts-all.php

Rate Law breakdown of Ammonia vs. Nitrogen dioxide

breakdown of ammonia rate doesn't depend on concentration so straight line indicating constant slope meaning amount of ammonia consumed remains constant regardless of how much or how little ammonia we have HOWEVER look at the same type of decomposition for Nitrogen dioxide and the rate changes based on concentration when there is a lot of concentration = fast rate = steep slope (high k) but as it gets lower = slope gets flatter = rate decreases until reaching horizontal line (barely any change to concentration) THE EQUATIONS AMMONIA AND NITROGEN DIOXIDE LOOK IDENTICAL, MEANING THERE IS NO WAY TO TELL RATE JUST BY LOOKING AT BALANCED EQUATION remember just because because you know the moles that react and form doesn't tell you anything about how fast or slow it takes

What Catalysts can NOT change?

catalysts are involved in kinetics and CANNOT change any THERMODYNAMIC PROPERTY at all MCAT LOVES TO TEST THIS does catalyst change equilibrium? No, just speeds it towards equilibrium does catalyst change Keq? No, keq = kf/kb a catalyst lowers activation energy meaning it speeds up both directions by the exact same amount does catalyst change Enthalpy (H)? No, enthalpy is the energy difference between reactants and products, catalysts only affect the RATE in lowering Ea does catalyst change Entropy (S)? No, does catalyst change Gibbs Free Energy? No does catalyst change yield? No

Rate Law for Catalyzed reactions

caveat: rate law would technically be addition of rate law of uncatalyzed plus rate law for catalyzed HOWEVER THIS CAN USUALLY BE IGNORED consider the Catalyzed reaction alone meaning the rate law is the same as normal catalyst is included as another reactant concentration to uncatalyzed rate law sometimes rate constant k is replaced with kcat (don't worry about difference if not presented) WHY DON'T WE CONSIDER UNCATALYZED REACTION? because the energy hump is much lower for catalyzed vs uncatalyzed meaning most molecules are taking the catalyzed and very few/none taking the higher energy required uncatalyed so rate is determined by catalyzed because they won't take higher energy most to all products come from catalyzed reaction uncatalyzed likely way to slow to contribute

Coordinate Covalent Bonds

covalent bond where both electrons SHARED are donated by one atoms "donor" molecules surround "recipient" molecule VERY IMPORTANT TO REALIZE THAT A COORDINATE COVALENT MUST HAVE A LONE PAIR OF ELECTRONS TO DONATE acts as Lewis Base Likewise the reciepient must have an EMPTY orbital in order to "receive" and share electrons (USUALLY TRANSITION METAL)

Catalyst vs. Enzyme

enzyme is a biological catalyst while catalyst is the general term enzymes are giant proteins folded into tertiary shapes that present an active site with specific shape for specific reactants ENZYMES STABILIZE TRANSITION STATES (lower Ea on graph making it easier to achieve) catalysts is the umbrella term enzyme is a specific catalyst all enzymes are catalysts but not all catalysts are enzymes (most are inorganic /metals)

practice problems to test understanding NOT MCAT type

http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Plink/probsets.htm http://www.sciencegeek.net/Chemistry/taters/directory.shtml

The graphs of Rate Laws (determining k from graphs) and multiple reactants?

https://www.chem.purdue.edu/gchelp/howtosolveit/Kinetics/IntegratedRateLaws.html IMPORTANT: GRAPHS WILL ONLY BE LINEAR WHEN THE REACTION HAS ONLY A SINGLE REACTANT OR WHEN PART OF MULTIPLE-REACTANT REACTION WHERE THE RATE IS INDEPENDENT OF ALL OTHER REACTANTS (other reactants are zero order not contributing to rate or in EXCESS meaning the concentration is always high so changes won't impact rate) MEANING TWO REACTANTS CAN'T BE IMPACTING RATE IF GRAPH IS LINEAR ONLY 1 WILL IMPACT THE RATE, so other has to be zero order or must be in excess so that change in concentration doesn't matter if reactants [A] and [B] graph 1/[A] is nonlinear what does that mean? it means that overall reaction is not in second order, nonlinear = both reactants may be contributing to rate graph ln[A] is linear what does that mean? linear means that only [A] is contributing to rate law, linear on ln means [A] is first order and B is either Zero order or must be in excess so that concentration difference over time doesn't contribute to rate more than one reactant that affects rate law will cause all graphs to be nonlinear the idea is I don't know what the rate order of reaction is, but I can make three graphs or data tables and check the slope of change take constant time and find the concentration (M) this is 1st graph 2nd graph take ln(M) for each point and graph over time 3rd graph take 1/(M) for each point and graph over time whichever one is linear means y/x is constant = k determines the order [A]/s = k = Zero order (not in nor contributing to rate law) ln([A])/s = k = First order 1/[A]t = k = Second order

How to calculate Order of each reactant (Rate Law)

https://www.chem.tamu.edu/class/fyp/stone/tutorialnotefiles/kinetics/ratecalcs.htm if concentration is x2 check rate with x2 or x2 x2 or x2 x2 x2 (keep consistent to make easier to keep straight) order of rates = power in rate law is determined experimentally with a table of values and multiple trials order is a measure that considers how amount concentration affects the rate determined experimentally (proof can't look at an equation and know orders of reaction RATE = proportion * [A]^order k=proportion constant = rate constant order determines if increase/decrease of concentration affects rate in 1:1 or 2:1 or 3:1 so [A]^1 if [A] increases by factor 2 the rate increases by factor 2 [A]^2 if [A] increases by factor 2 the rate increases by factor 4 [A]^0 = 1 (rate=k[B]) if see A in reaction but not in rate law it means that concentration of A doesn't affect rate of reaction (whatever A is high or low the rate remains the same with experiments and trials can see how change in concentration would change the rate (AGAIN THE MOLE RATIOS DO NOT TELL YOU RATE) find two trials where desired [reactant] changes, and all other reactants remain constant note the factor that [reactant] changed by also note the factor that rate changed in same two trials X^y=Z [A]^order = rate solve for y to get order x=factor [reactant] changed y=order of reactant remember that any number to power of 0 = 1 ZERO ORDER: if [A] is tripled, rate is unchanged (doesn't depend on concentration) FIRST ORDER: if [A] is tripled, rate is tripled (rate = k[A]) if increase of [A] is + 1/2 then increase of rate is + 1/2 SECOND ORDER: if [A] is tripled, rate is *9 that is rate increases by square of concentration increase (rate = k[A]^2) if [A] increased by + 1/2 or 0.5 then rate is increased by + 1/4 or 0.25 Exp: 1 [A](M): 0.4 rate M/s: 8.0*10^-3 and Exp: 2 [A](M): 0.2 rate M/s: 4.0*10^-3 reactant changed by factor 2, rate changed by factor 2 meaning first order Exp: 1 [A](M): 0.75 rate M/s: 0.0032 and Exp: 2 [A](M): 1.50 rate M/s: 0.014 reactant change by factor of 2 but rate looks like change of 4 meaning second order Look at the FACTORS of change NOT the difference reactant changed by factor of 2 rate changed by factor of 2 [reactant]^order = rate 2^order = 2 order = 1 after finding order of reactant, the "overall order" is the sum of all exponents in rate law z=factor that rate changed and once you know the rate orders as well as concentrations and rates can solve for k rate constant for that specific reaction rate = k[reactant]^order

Purpose of rate orders

not all reactions are the same, just because double the reactant doesn't mean double the product the concentration of reactant may play a huge or no part at all when a single molecule decays it requires no collision to react, does increasing concentration affect rate? yes, if there are more particles decaying there is more product (rate of decay 1 in a million, having 100 million would have 100 while 200 millioin would have 200, doubling the rate) (FIRST ORDER) if a catalyst is already working as fast as it can, does increasing concentration affect rate? No, catalyst is already at max rate every reactant is then added in excess providing no additional change in multi-step rate is determined by slowest step=rate determining step A step is slow and B step is fast increasing concentration of B will increase B but negligible on overall rate (still waiting for slow step) increasing concentration of A provides the largest benefit to rate

Rates of Multi-Step reactions

rate law is ALWAYS determined by slowest step k for entire net rate is taken from slow step when slow step is first everything is simple rate law for entire reaction is same as rate law for slow step BUT what if slow step is second? well, the products of first step are reactants in the second slow step so the rate law for the overall reaction is STILL the rate law for slow step https://www.youtube.com/watch?v=MEEg7aHqk6A

Covalent Bonding

usually formed between two non-metals and involve SHARING of electrons within bond (SHARING DOES NOT HAVE TO BE EQUAL, CAN BE POLAR WITH FORMAL CHARGE) besides completely transferring, atoms of similar electronegativities can SHARE electrons (have to be similar atoms of similar strength for electrons) (each can donate 1 and share the 2 together) sharing doesn't need to be equal (and isn't due to differences in electronegativity) can imagine an Na and Cl coming together in neutral state, maybe there was an instant where they shared, but higher electronegativity of Cl pulled the electron completely away giving negative and positive charge resulting however it is a an over reliance that atoms simply attempt to reach noble gas configurations. some atoms like Boron (3 valance e- forming 3 covalent bonds and having 6ve-) and Phosphorous (can have 5 pairs of electrons exceeding octet) (and DO NOT reach noble gas config yet are purely stable THERE IS A SERIOUS MISMATCH BETWEEN LEWIS DOT (noble gas config) AND MODERN ELECTRONIC STRUCTURE (1s2s2p and boxes of energy level height) a carbon according to lewis dot has 4 UNPAIRED valance electrons BUT modern box 1s2 2s2 2p2 only has 2 UNPAIRED (s is slightly lower energy than p so all s is filled) SO WHY DOES C WANT TO FORM CH4 OVER CH2? PROMOTING ELECTRON FROM S TO P because the release of energy is greater (twice as much making the molecule more stable) there is only a small energy gap between 2s and 2p orbitals so it only takes small amount of energy to promote electron from 2s to 2p resulting in 2s1 2s3 (with Hund's rule every orbital is now unpaired) great now we have 4 unpaired orbitals ready to bond however there is a problem: in methane all 4 of C-H bonds are energetically identical that means the 4 orbitals (1s and 3p) need to be identical orbitals HYBRIDIZATION electrons rearrange to form four IDENTICAL HYBRID ORBITALS: sp3 when two atoms bond, the orbitals merge to produce a new molecular orbital (the following occurs: promotion of electrons, hybridization followed by formation of molecular orbitals which is applied to any covalently-bound molecule) even if all p orbitals already have an unpaired e- and s was filled with 2 e-, the orbitals would still hybridize into sp3 and we could predict that this molecule having 1 paired and 3 unpaired equal sp3 atomic orbitals would then form 3 molecular orbitals as in PCl3 now in PCl5 can also be explained by molecular orbital (but can't be explained by Lewis Dot) 3s2 3p3 3d0 one of the electrons from 3s2 can be promoted to 3d making 5 unpaired electrons 3s1 3p3 3d1 which then hybridize to the same energy level creating 5 equal sp3d orbitals why this promotion, to a d orbital? because this extra energy investment is more than paid off with much more energy release when bonds form (electrons are not seeking and considering their investments its just that when they do something that results in extra stability they are not likely to revert back) http://www.chemguide.co.uk/atoms/bonding/covalent.html#top

Empirical vs. Molecular formula

Empirical is the smallest RATIO formula of elements for a compound. represent the lowest possible moles (same mole-to-mole ratio between elements Molecular is the ACTUAL formula for a compound. a multiple of the empirical formula CH2O is the empirical of glucose C6H12O6 is the molecular of glucose

Equilibrium and Kinetics

Equilibrium is a measure of concentration and how the concentrations change when system is disrupted form outside Kinetics deals with how fast rate of reaction is, BUT NOT the concentrations or their moles on an energy coordinate diagram, equilibrium would deal with starting and ending concentrations (at slightly different energies (lowest energy is preferred and would have higher concentration than higher energy) but at equilibrium the concentrations would stop changing as rates of forward and back are = kinetics deals with that activation energy at equilibrium Gibbs free energy will be zero so reaction doesn't proceed spontaneously in either direction Keq is a mathematical number describing equilibrium determining the concentrations that will result (BUT NOT THE RATE) a high Keq can actually be very slow (hence catalysts) all a high Keq tells is that at equilibrium the concentrations of products will be much higher than reactants

Shapes of Molecules and Ions

First make sure to look at arrangement of atoms COCl2 C= forms 4 covalent bonds O= forms 2 Cl= forms 1 The group/family number determines valence electrons ELECTRON PAIR REPULSION THEORY shape of molecule or ion is determined by arrangement of electron pairs around central atom (the valence level) 2 groups no l.p. = linear (BeCl2) angle is 180 (max electron distance away=most stable) 3 groups no l.p. = trigonal planar (BF3) angle is 120 on same plane 4 groups no l.p. = tetrahedral (CH4) (NH4+) angle is 109.5 4 groups 1 is l.p. = pyramidal (NH3) angle is 107 (lone pair on top provides stronger repulsion than bonds) 4 groups 2 is l.p. = bent (H2O) angle is 104 5 groups no l.p. = trigonal bipyramidal (PF5) 120 and 90 and 180 (linear + tirgonal together) 5 groups 2 l.p = T- shaped (ClF3) 120 and 90 and 180 AS FOR WHERE THE L.P. ELECTRONS GO, REMEMBER THAT L.P. HAVE THE STRONGEST REPULSION SO ANGLE FOR THEM NEEDS TO BE HIGHEST BUT ALSO NEED TO MINIMIZE L.P. - BONDING REPULSION can consider that angles above 90 deg are negligible, first put l.p farthest away (180 from each) and count how many l.p - bond repulsions at 90 or less (3 and 3= 6) if this is high, then try l.p a little closer (120 from each) and l.p- bond repulsions (2) this arrangment is most stable for trigonal bipyramidal when l.p are at 120 6 groups no l.p = octahedral (SF6) all at 90 deg linear and square planar together 6 groups 2 l.p = square planar (XeF4) l.p will be at 180 while rest at 90

Understanding Chemistry Bonds (EMP important)

Ionic bonding Covalent bonding Coordinate (dative covalent) bonding Electronegativity Shapes of simple molecules and ions Metallic bonding van der Waals forces Hydrogen Bonding Bonding in organic compounds http://www.chemguide.co.uk/atoms/bondingmenu.html

Reaction Quotient K and Q

K talks of conditions at equilibrium and determines goal concentrations or partial pressures that forward and backward rates will approach aA + bB <-> cC + dD at K, rate (aA + bB -> cC + dD) = rate (cC + dD -> aA + bB) Q the Reaction Quotient describes reaction right where it currently is at (not necessarily at equilibrium) aA + bB <-> cC + dD again rate is determined by how much mass is available to react (concentration via law of mass action) Q = [C]^c*[D]^d/ [A]^a*[B]^b only for gas or Aqueous state components (pure liquid or pure solid has an activity of 1 which can be omitted) Q is at specific time whether at beginning before anything has reacted or much later it is useful because we can compare current Q to K to predict the net direction of reaction Q=K then reaction is currently at equilibrium Q is not equal to K then, reaction is not at equilibrium but will go in direction towards equilibrium IMPORTANT Q = products over reactants Q>K currently more products, reaction will produce reactants to lower Q back to K Q<K less product, to raise Q to K reaction produces more product ALSO IMPORTANT, take a look at the value of K if K is greater than 1 then know that there is more products than reactants (at equilibrium) if K is less than 1 then know that there is more reactants than products with K and nothing else, I know which side has more or less energy (stable

Kinetics and Thermodynamics

Kinetics: how fast reaction proceeds (KE and activation energy and orientation of molecules including temp as avg of KE (some molecules have enough energy others do not) increasing the temp puts a larger percentage of molecules over the hill of activation energy allowing faster rate and increasing chances of collisions in the right orientation KINETICS= RATE, CATALYSTS, ENZYMES, ENERGY OF ACTIVATION, REACTION ORDER, TRANSITION STATE Thermodynamics: potential reactivity (no mention of time or rate) but the difference in energy between reactants and products bond energies are high = more stable lower energy (enthalpy represents bond energies) entropy deals with input or release of energy (endo/exothermic) to create order or release into disorder Gibbs takes both enthalpy (bond energy) and entropy to measure free energy of entire system THERMODYNAMICS: Keq, Q, ENTROPY, ENTHALPY, GIBBS FREE ENERGY, SPONTANEITY, DIFFERENCES IN ENERGY BETWEEN REACTANTS AND PRODUCTS THERE IS A WALL OF SEPARATION BETWEEN THERMODYNAMICS AND KINETICS (except for temperature is only thing that changes Keq high thermodynamic doesn't mean high kinetic just because reaction is fast doesn't mean more stable or higher yield

Temperature and Le Chatelier's Principle (and Keq)

Le Chat: equilibrium will shift to counteract changes (meaning if temp goes up, equilibrium shift to bring temp down) need to know if heat is being ABSORBED or RELEASED (determines how to change temp) Delta H or enthalpy is given (always referring to left to right side of reaction) +H = energy is input (endo) (left side) A + B + H <-> C + D -H = energy is leaving as heat (exo) (right side) A + B <-> C + D + H treat temperature like concentration, if increasing temperature, shift away from temperature +H = temp on left so shift away to right -H = temp on right so shift away to left if decreasing temp, shift towards temp +H = temp on left, shift to left -H = temp on right, shift to right if temp increases favor products away from heat to lower temp if temp decreases favor products with heat to raise temp INCREASING TEMP FAVORS ENDOTHERMIC REACTIONS ,system counteracts change by absorbing heat (lowers temp) DECREASING TEMP FAVORS EXOTHERMIC REACTIONS, system counteracts change by releasing more heat (raises temp) Now consider why we would use higher temperature even though it doesn't favor the products we want because the lower the temp, the slower the molecules and the slower the reaction, even if by lowering the temp you shift the equilibrium position to desired place, it may take years for reaction to reach desired equilibrium, so typically compromise by favoring a less than ideal equilibrium but a fast reaction TEMP NOT ONLY SHIFTS EQUILIBRIUM, IT ALSO CHANGES THE RATE CONSTANT (why because Keq=kf/kb and while changing the energy of transition state gives both kf and kb an equal benefit, changing the energy of temp will be different for kf and kb because temp is also a reactant that favors one or the other (catalyst alters Ea but favors both equally) exothermic (heat on right) : increasing heat->slows reaction rate endothermic (heat on left) : increasing heat-> speeds reaction rate HABER process of turning Nitrogen and Hydrogen gases into Ammonia is exothermic (temp on right side), takes a high temp to make reaction faster at expense of a 15% yield per cycle (unreacted gas is recycled back into chamber so efficiency is still high at 98%) https://www.quora.com/What-factors-affect-the-equilibrium-constant

Metals vs. Non-metals

METALS: LARGER atoms with loosely held electrons love to lose e- and form POSITIVE ions lustrous, ductile, malleable, excellent Conductors of heat and electricity high melting points (tend to form metallic bonds where heat can easily transfer in and out) form ionic bonds with nonmetals NON-METALS: SMALLER atoms with tightly held electrons love to gain e- and form NEGATIVE ions poor conductors of heat and electricity (tend to form covalent bonds where two atoms share electrons tend to solid or liquid or gas have lower melting points than metals

Periodic Table and Characteristics of the Elements

PERIOD: horizontal left and right (determines principle quantum number) GROUP: vertical up and down (determines outer shell chemical properties and nonmetal metal ALKALI METAL: group 1 and 1 e- away from full outer shell configuration so extremely reactive, soft silvery, not found in pure state but bound ALKALINE EARTH METALS: group 2 and 2 e- from full outer shell config so very reactive TRANSITION METALS: starting on period 4 and represented by d block excellent conductors can freely rearrange or give and take electrons LANTHANIDES: upper row of f block ACTINIDES: lower row of f block HALOGENS: group 7A 1 e- away from full outer shell configuration NOBLE GASES: group 8A are in full outer shell configuration and non reactive s-block: first two families/groups p-block: last six families groups d-block: the transition metals f-block: "inner transition metals" occurring inbetween s and p block on periods 6 and 7

Bonding and Anti-Bonding Orbitals

PUT PICTURE OF BONDING AND ANTIBONDING antibonding orbitals are higher in energy than bonding orbitals (less stable) bonding orbitals have electrons that are "in phase" or "attractive" antibonding orbitals have electrons that are "out of phase" or "repulsive" weakens the chem bond between two atoms (e- in antibonding are outside bonding region and act to pull away nucleus from the other) and raises energy of molecule relative to separated atoms when same sign on same side (not charge just similar wave function) then they are bonding BONDING AND ANTIBONDING IS A WAVE PROPERTY OF ELECTRONS HOW THE CAME TO BE when two similar atoms are separated they can have identical atomic orbitals, but as they get closer to each other their electron clouds and wave functions begin to overlap meaning the electrons can no longer remain in the same address (according to Pauli Exclusion Principle) THEREFORE when two identical orbitals combine, they split into two lower and higher orbitals relative to original bonding causes reduction or release of energy (stable) antibonding causes increase or storage of energy (unstable) antibonding occurs when electron density is pulled away from between atoms (where bonding occurs) where they would be if the atoms were separate since bonding is lower energy it will fill first (Aufbau) and then antibonding will fill BUT antibonding orbital is more antibonding than the bonding orbital is bonding meaning when all is filled, combined atoms will be unstable in polyatomic atoms, some orbitals that bond will be bonding while others antibonding, if there are more bonding than antibonding the Molecular Orbital is bonding https://en.wikipedia.org/wiki/Antibonding_molecular_orbital

Rules for Electron configurations

Pauli Exclusion Principle: no two e- can have same 4 quantum numbers Aufbau (build up) Principle: lower energy orbitals is filled first Hund's Rule: when multiple orbitals have same energy, one goes in each before doubling up to minimize repulsion

Calculating Percent Mass

Percent Mass = (Mass Element/Mass of compound)*100 in C6H12O6 what is percent mass of C? Mass: C = 12 = 12*6 = 72 H=1 = 12*1 = 12 O=16 = 16*6 = 96 Total = 180 72/180= 40% (always divide numerator by denominator NOT larger by smaller) in H2O what is percent mass of H? H= 1 = 2*1= 2 O= 16 Total = 18 2/18= 1/9= 10%

Deriving Formula from Percent Mass

Percent mass can ONLY give Empirical Formula (because based on percentage not the actual, we have to assume a total of 100g) but if MW is given (the actual total mass) we can take Empirical and derive the Molecular 1. percent becomes grams (assume 100g total so that 15% becomes 15 grams) 2. grams needs to be converted to moles to compare apples to apples 3. the element with the lowest moles is divided into the rest (ratio of lowest to highest) and this ratio serves as the empirical formula If subscripts are not at lowest common denominator, reduce If given actual MW then can take Molecular Weight/Empirical Weight which is a ratio that gives whole number to multiply each subscript of empirical to get molecular

Partial Pressure of gases equilibrium (Kp)

Pressure is determined by moles of gas molecules (more moles = more bouncing against the walls) if ever wanted to change number of moles of gas, use pressure Mole Fraction remember that pressure is determined by the numbers of moles of a gas when a mixture of gases, each individual gas exerts a partial pressure Xa= number moles gas a/ total number of all gas moles what fraction of pressure comes from a specific gas is determined by the number of moles if a mixture of 1 mole Nitrogen and 3 mole Hydrogen then total is 4 gas moles Partial pressure of Nitrogen is 1/4 = 0.25 Partial pressure of Hydrogen is 3/4 = 0.75 almost like a percent mass where all mole fractions add to one Pressure of gas A = mole fraction A * total pressure if mixture of 20 moles Nitrogen, 60 moles Hydrogen, 20 moles Ammonia for total of 100 moles of gas at 200 atm pressure What are the partial pressures of each gas? the ratio of moles determines the ratio of pressure nitrogen: 20/100 = 0.2 mole fraction partial pressure of nitrogen: 0.2 * 200 = 40 atm hydrogen: 60/100 = 0.6 mole fraction partial pressure of Hydrogen: 0.6 * 200 = 120 atm ammonia: 20/100 = 0.2 mole fraction partial pressure of ammonia: 0.2 * 200 =40 atm notice how all partial pressures add to total 200 atm REMEMBER THAT PRESSURE IS DETERMINED BY NUMBER OF MOLES, because pressure comes from molecules bumping against the wall, the more molecules = more pressure and in a mixture of gases the mole ratio determines how much pressure each gas exerts KEY POINT: partial pressure in mixture = pressure gas would exert if alone occupied same container 20 moles of nitrogen would exert the same 40 atms regardless of being alone or with hydrogen and ammonia in same container if gas A and gas B are in two different containers, gas A is creating pressure when its molecules hit the walls of its container likewise gas B does the same creating pressure when molecules hit container if gas A and B are put in same container their individual partial pressures don't change (BUT THE TOTAL PRESSURE HAS INCREASED AS THERE ARE MORE MOLES IN CONTAINER) if adding gas while keeping constant total pressure, then partial pressure would of each gas would decrease because partial pressures have to add up to whole pressure the whole point is to understand that presence of multiple gases in same space DOES NOT affect the pressure contribution of each other Kp equilibrium expression aA(g) + bB(g) <-> cC(g) + dD(g) at equilibrium point, use the partial pressures Kp = PC^c * PD^d / PA^a * PB^b note the difference between Kc and Kp Kp does NOT use concentration (for gas), but relies on the partial pressure (a measure of moles for gas) because pressure relies on gas phase don't include solids or liquids

Metallic Bonding

THE VALENCE e- ARE SO WEAKLY HELD (LARGE SIZE) THAT NEIGHBORING NUCLEI INTERCHANGE THEM READILY metals have HIGH Melting points and Boiling points compared to nonmetals this is due to metallic bonding where molecular orbitals form (not unlike covalent) (only hold two so has to be a large number of them) and electrons become delocalised freely moving between all the orbitals of a piece of metal NOT FORMING IONS, METAL IS MADE OF ATOMS (because the e-s are not lost from atoms) BUT THE POSITIVE CHARGE OF PROTONS IS STRONGLY ATTRACTED TO THE SEA OF DELOCALIZED E- Na electron will not leave Na but will delocalize Mg two electrons will delocalize so Mg will have smaller nucleus (after "donating") and will have more partners to closer to it D BLOCK transition metals can involve not only their 4s orbital but the 3d orbitals, the more electrons you can involve the stronger the sea of electrons tend to be after the size of atoms gets smaller to a certain point, electrons no longer delocalize (nonmetals)

Factors affecting Rate

Temp concentration catalyst temp increases the speed of molecules giving more KE and more collisions, have higher proportion of molecules with more energy than Ea increases the rate of reaction concentration provides more molecules to react catalysts bring molecules together in correct orientation lowering the energy needed to react ACTIVATION ENERGY IS DIFFERENCE BETWEEN REACTANTS AND PRODUCTS

Condosity

The condosity of a solution is the concentration (molarity) of an NaCl solution that will conduct electricity exactly as well as the solution in question MORE METALLIC THAN SODIUM = MORE CONDUCTIVE = SODIUM NEEDS HIGHER CONCENTRATION TO MATCH LESS METALLIC THAN SODIUM = SODIUM DOESN'T NEED AS MUCH TO CONDUCT THE SAME ELECTRICITY 2.0 M KCl K is lower in periodic table than Na, K is larger in size, ability to disperse electrons more = more metallic if K is more metallic than Na, then need more Na to match M of Na > 2.0 M 3.0 M LiCl Li is above Na on periodic table, Li is smaller in size, can't disperse electrons as much as Na = less metallic Li is less metallic than Na so need less Na to match Li M of Na < 3.0 M

Transition Metal Color Production vs. traditional electron falling to produce light

Transition metals have d-orbitals d-orbitals absorb all light EXCEPT for color observed (color observed is reflected light (not because of excited e- falling to resting position) the traditional way is that electrons fall closer to nucleus releasing potential energy as photon with frequency (E=hf) meaning color

Trends Summary

atomic size decreases across period (Zeff) increases down group Electron affinity is greatest for smallest atom and weakest for largest atom Electronegativity is same (greatest for smallest atom and weakest for largest Ionization Energy is small for a large atom and large for a small atom understand the conceptual differences between each characteristic.

Atomic Weight vs. Molecular Weight vs. Molar Mass

atomic weight: the weighted avg of atomic masses of different isotopes of an element (mass of one mole for an atom) molecular weight: taking all the atomic weights of a compound and summing together Molar Mass: the mass for one mole of substance mole: lit "a small mass" where C12 is the standard where 1 mole of this substance is 12 grams the mole for other substances would have the same amount of stuff or number of particles as in 12 grams of C12 1/12 of a mole of Carbon became the official gram (amu) a mole of chlorine with a mass of 35.5 grams really means that that the MASS OF CHLORINE IS 35.5 TIMES GREATER THAN THE MASS OF 1/12 OF A MOLE OF CARBON 12 Avogadro's Number: by definition a mole always contains 6.022 * 10^23 of particles (atoms or molecules or ions) A MOLE IS THEREFORE A 6.022 *10^23 OF ANYTHING just as a dozen means 12 of something and a pair means two of something when we have 6.022*10^23 we have a mole of something 6.022*10^23 atoms of carbon gives mass of 12 grams 6.022*10^23 atoms of Hydrogen has a mass of 1 gram 6.022*10^23 atoms of Calcium has a mass of 40 grams

Equilibrium

balance for REVERSIBLE reactions the forward rate produces reactants for the backwards rate so eventually as more backward reactants are formed, the backward rate rises and forward rate decreases but if the backward rate increases to much it more of its reactants and creates products that forward rate can then use so then the backward rate decreases and the forward increases EVENTUALLY WHAT HAPPENS IS THE FORWARD AND BACKWARD CONCENTRATIONS KEEP MOVING UNTIL REACHING A POINT WHERE THE RATES ARE EQUAL (concentrations are stable but do not have to be equal) important to understand that equilbrium doesn't mean the forward and backward reactions no longer occur, they very much are but since the rates are the same we see no net difference in concentrations That is why we say DYNAMIC EQUILIBRIUM orange and blue squares that reversibly change into one another orange changes to blue at rate of 1/6 blue changes to orange at rate of 3/6 if there are twelve squares, can use a dice where 4,5,6 represents the change of blue to orange and 6 represents the change from orange to blue because the rates are constant, equilibrium is achieved and will see a high concentration of orange to blue and low concentration of orange that relatively doesn't change (the higher the sample size the more accurate this prediction will be, why use large sample sizes in testing) If reaction was blue <-> orange, equilibrium point would lie more towards orange

Le Chatelier's Principle: Concentration

changes in CONCENTRATION, TEMPERATURE, PRESSURE affect the position relative to equilibrium which counteracts the change (THIS IS BECAUSE THE EQUILIBRIUM CONSTANT IS CONSTANT unless changing temperature which is only factor that moves equilibrium position A + B <-> C + D increasing concentration, will cause equilibrium point to move to counteract increasing concentration More B = equilibrium shift to right (decreases B) less A = equilibrium shift to left (increases A) if there is more of B then more likely to react and become C and D if there is less A then less to react and more likely that C and D will form A if you continually add or take (equilibrium is readily established in closed systems) then equilibrium point keeps on shifting making it possible to make an equilibrium into a one way reaction THE CONTACT PROCESS (making sulfuric acid) again since oxygen is free and in air can use plenty of it to influence equilibrium point in making sulfur trioxide (from sulfur dioxide and oxygen), but in enclosed space it is better to have 1:1 ratio for the sake of catalyst surface area

Co-ordinate (Dative Covalent) Bonding

covalent is when two atoms share a pair of electrons atoms are held together because the e- pair is attracted by both the nuclei (MUST HAVE TRANSITION METAL AND OTHER GROUP MUST HAVE L.P. of ELECTRONS) in simple covalent bond, each atom supplies one electron to the bond in coordinate bond (divalent covalent) the electron pair is shared by both but only one of the atoms provided both electrons NH3 + HCl -> NH4Cl the Nitrogen provides two electrons to the hydrogen ion (no electrons) from the Cl leaving Cl- remember how Boron in BF3 doesn't fulfill octet, described as electron deficient NH3 has a lone pair that can donate and share with Boron making N+ and B- (instead of using + and - can use arrow to indicate where both electrons came from) EX of AlCl3 AlCl3 will quickly sublime at about 180 deg, if it was made of ions, it would have very high melting and boiling point because attraction between positive and negative charge is strong, therefore AlCl3 must be covalent (weaker than ionic) and is electron deficient Al and B are in same group AlCl3 forms a dimer becoming Al2Cl6 via two coordinate bonds donated by Cl onto Al (the lone pair donates) HYDRATION Water can also donate its two lone pairs to metal (sometimes the attraction of water to charged ions are so great that a formal bond is made called hydrated ion) Al will hybridize 6 empty orbitals (3s 3pxyz 3d 3d) for water to donate to release the most energy (why six) because that is usually the max water molecules that can fit around an aluminum (and most metal ions) if there was room it would make as many as there are water molecules with lone pairs available (metals with d orbitals are very flexible and good conductors of electrons) 6 is also the magic number of electron stability in a double or triple bond it is possible that one of them could be coordinate covalent as in Carbon Monoxide CO

Cations vs. Anions

don't lose protons, the number electrons change when forming an ion proton and electron are (+ and -) and cancel out when same number if adding e- have more e-s than protons then anion if taking away e- and have more protons than e-s then cation ANION: more electrons than protons CATION: more protons than electrons metals LOSE electrons to form full outer shell (gets smaller reverting back to smaller energy shell closer to nucleus) nonmetals GAIN electrons to fill their outer shell (gets larger by adding more higher energy electrons further away from nucleus eventually completing its outer shell a full shell is very stable once reached, most likely will not react anymore

Mass of atomic subparticles

e- = 9.1*10^-31 kg= 0.000548 amu proton= 1.67*10^-27 kg= 1.007 amu neutron= 1.67*10^27kg= 1.008 amu

Electronegativity

electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons (POLARITY gives formal charge) Pauling scale used as comparative tool (qualitative, there is no measure of energy) if equal electronegativity: same tendency to attract bonding pair e-s so they will be found ON AVG halfway between atoms which is usually true when atoms are same more electronegativity = more pulling closer to itself and because of more electron density it becomes relatively more negative while less electronegative has electron density pulled away becoming more positive polar bond: when charge is separated as electron density is polarized with extreme electronegativity differences, ions form as one atom strongly takes electrons (both become stable as a result metal and nonmetal) UNDERSTAND that there is no clear cut division between covalent and ionic bonds as covalent molecules experience polarization and even in NaCL the Na has not completely lost control of its electron (remember electrons are in molecular orbital and are moving around all the time within that orbital) when considering a molecule consider the direction because polarity is a vector and molecule with polar bonds can turn out to be non polar ALSO keep in mind the strength of polarity which means only same atom polarity will "cancel out" PERIOD TRENDS strength of proton charge, adding protons increases electronegativity while adding shell levels increases distance and shielding electrons that decrease strength of proton charge

Ionic Bonding

elements desire noble gas configuration (most stable lowest energy) (unless in d bloc, they are ok with having sea of electrons) metals lose electrons while nonmetals gain electrons (ALL IONIC BONDING RESULTS IN STRONG BONDS MEANS LIKELY SOLIDS AT ROOM TEMP) NaCl is a salt (salts are solids) causes difference in number protons and electrons giving charge charge can experience electrostatic interaction like (gravity and mass) where the greater the charge the stronger the interaction and the more energy that is released upon bonding (to break requires input of energy) but there is a down side (why don't atoms form the most negative or most positive if resulting energy will be lowest?) because energy is needed to remove electrons from atoms the more electrons are removed the greater (drastically) the ionization energy increases to the point where the amount released by bonding isn't large enough to cover it. http://www.chemguide.co.uk/atoms/bonding/ionic.html#top

Gamma Emission

emitted as a byproduct of the types of decay above ALL RADIOACTIVE DECAY IS USUALLY ACCOMPANIED BY GAMMA EMMISION after decaying by alpha or beta, the resulting nucleus may have too much energy to be completely stable when in the nucleus, proton(s) and neutron(s) rearrange maybe get closer they release energy in form of very high frequency (high energy) gamma wave nothing is added or taken away light leaves as a result of increased energy stability in nucleus NO CHANGE IN NUMBER OF NUCLEONS (protons and neutrons don't change only rearrange position to release energy in form of light) travels at the speed of light (it is light)

Energy Levels

energy levels represent energies of electrons in an atom. quantized (discrete increments) meaning graph looks like staircase that jumps and not a ramp that gradually climbs because energy levels are quantized and not gradual, cannot cause electron to move up to next energy level until adding an amount of energy = to difference in energy between current level and higher energy level if energy is lower than threshold or difference between energy levels, then the energy is simply refracted out with the same energy it came in with (photoelectric effect of photons) or it passes through without absorption when dropping to lower level, the energy released is always EXACTLY equal to the difference between energy levels (if release red light, then will always release red light) light looks like it exists on a continuous spectrum ROY G BIV 700 nm - 400 nm (low to high frequency) red is lowest energy (below that is light that can't be seen) violet is highest energy (above that is light that can't be seen) BUT light emitted when put through a prism shows not continuous light but discrete or specific components of light. which provides evidence that electrons are likewise not continuous in energy but have discrete quantized energy levels so to find E released simply take the difference between energy levels E= initial-final to find how much energy is released or absorbed (when final is more than initial then absorbed and no light released, when final is less than initial E gives energy of light released) E=hf (IMPORTANT TO NOTE THAT WHEN AN ELECTRON IS FREE ITS ENERGY IS 0, REMEMBER HOW ELECTRON GAINS ENERGY AS IT MOVES AWAY FROM NUCLEUS, THERE IS A LIMIT WHERE n=infinity and electron is now free having 0 energy that means we are working with negative and less negative numbers to the point of 0 meaning ground state is most negative while higher energy levels are less negative (more positive energy) and the most stable orbital is one with the lowest energy (most negative) it takes more energy to go from n=1 to n=2 but takes less energy to go further away from nucleus as a result going closer to nucleus involves releasing more energy= higher frequency= lower wavelength the energy levels of each atom are unique allowing the line spectrum to be used as a fingerprint https://www.youtube.com/watch?v=CZHznHR1pB4

Limiting Reagent

equation must be balanced to serve as recipe book limiting reagent determines how much is reacted and how much is formed all reactants must be converted to moles (because coefficients of recipe refer to moles) compare moles have to moles needed for one cycle (divide moles have by coefficients, this gives the number of times can run the cycle) the lower result will run out first and is the limiting reagent, once it runs out, the reaction can no longer repeat because there is nothing to react with IT MAY NOT BE THAT THE LEAST MOLES OR GRAMS IS THE LIMITING REAGENT (pay attention to balanced equation and see how many cycles each can go through before running out) if I have 8 tires and 3 steering wheels when making a car, it takes 4 tires and 1 steering wheel to make a car I will run out of tires before steering wheels (even though I have more tires than steering wheels) THE BALANCED EQUATION IS VERY IMPORTANT CH4 + 2O2 --> 2H2O + CO2 if I have 1.5 mol O and 1 mol methane what is limiting reagent? I can see that I will run out of O before methane 1.5/2= 0.7 cycles O 1/1= 1 cycles methane the limiting reagent determines the moles reacted (again if limiting runs out no more reaction even if one of the reactants is plentiful) with moles of limiting reagent can convert using mole ratio to moles of reactant that react and moles of product formed

Pressure and Le Chatelier's Principle

equilibrium shifts to counteract change Pressure is caused by GAS molecules hitting the sides of their container, the NUMBER of GAS MOLECULES determines PRESSURE so INCREASING PRESSURE of system causes equilibrium to favor decrease in pressure that is favor side with LESS MOLES OF GAS that lowers the pressure DECREASING PRESSURE of system causes equilibrium to favor increasing pressure by favoring side with MORE MOLES OF GAS just like temperature, write pressure on the side where it is most making it easier to see how increasing or decreasing will change equilibrium A(g) + 2B(g) pressure <-> C(g) + D(g) if more pressure, equilibrium will minimize and favor right side if less pressure, equilibrium will maximize and favor left side SOLIDS AND LIQUIDS DON'T CONTRIBUTE TO PRESSURE, INCREASING THEIR CONCENTRATION DOESN'T AFFECT PRESSURE AT ALL, BUT THE NUMBER OF GAS MOLECULES IN AN ENCLOSED SPACE DETERMINES PRESSURE AS GAS IS FREE TO BUMP ALL OVER THE WALLS and more moles of gas means more crowded bumping QUESTION what if both sides have same number of moles of gas molecules? as in... A(g) + B(l) + C(g) <-> 2D(g) + E(s) 2 moles gas on left = 2 moles gas on right well then pressure would NOT affect equilibrium position at all HABER Process N2(g) + 3H2(g) <-> 2NH3 (g) increase pressure, equilibrium shifts to lower the pressure = favor side with less gas moles (right has 2, left has 4) increasing pressure brings molecules closer together increasing collisions and rate of reaction (why don't use highest pressure possible, because the economic cost of maintaining high pressure)

Quantum Mechanics

every individual electron has its own unique "address" or "location" the "address" consists of four numbers like 1st the street name (level shell) (period) 2nd the house or building number (subshell or orbital) (s block, p block d block f block) 3rd the room (orientation of orbital) (which orientation) 4th which of two beds (spin) (up or down) VERY COOL IMAGE CONNECTING PERIODIC TABLE TO ALL QUANTUM NUMBERS http://www.chemistryland.com/CHM151W/07-Atomic%20Structure/Spectra/PeriodicTableWithQuantumNumbers.jpg http://www.chemistryland.com/CHM151W/07-Atomic%20Structure/Spectra/PeriodicTableWithIndividQuantumNumbers.gif

Why do large atoms stabilize charges better and why can't they form pi bonds?

form weak pi bonds because their p orbitals are harder to overlap due to increased size larger atoms can have d orbitals that can "house" extra electrons (good conductors)

Electron Capture

gain an electron, proton becomes neutron by capturing an electron, in nucleus convert proton to neutron (when neutron = proton + electron, adding an electron to proton makes a neutron) the opposite of a beta decay e- enters nucleus, proton becomes neutron

Electrolytes

good electrolytes break up into cations and anions when dissolved in water more soluble = better electrolytes strong electrolytes ionize completely (strong acids/bases, and salts) weak only partially (weak acids/bases) PURPOSE OF KNOWING need to be able to know what dealing with, whether will exist as compound or as ions HCN or NaCN? HCN exists as a gas, but NaCN will exist as an ions Na+ and CN- but not as a gas https://www.stolaf.edu//depts/chemistry/courses/toolkits/121/js/naming/elec.htm

Half life application is more than age of fossils and radioactive decay

half life is amount of time needed for a reactant concentration to decrease by half compared to its initial concentration it represents probability, if looking at specific C14 atom (1/2 life: 5740 years) it can decay 1 day after or may not decay even after 1 billion years but with larger sample size and law of large numbers, more and more will find that 50% will decay after 5740 predicts concentration of substance over time (determine drug absorption by seeing how much decreases after absorption or elimination VERY IMPORTANT half life is varied between different type of reactions zero order kinetics: rate of reaction does not depend on substrate concentration (implying a straight slope line regardless of high or low concentration) slope is negative and constant and half life time decreases (because rate doesn't change) every time half life depends on initial concentration (more initial means longer half life) first order kinetics: slope continually decreases as concentration decreases approaching 0, the amount of time between half lives is the same independent of any initial concentration (because rate changes to keep rate of decay constant) second order reactions: like 1st order, 2nd order decreases rate with time towards 0 however the rate decreases much faster, and the half life time increases (depends on initial concentration) (more initial means shorter half time)

Inorganic Nomenclature

http://faculty.seattlecentral.edu/ptran/experiments/chem140/nomenclature.pdf primarily the naming of ionic compounds GEN IONIC COMPOUNDS name cation first then anion Calcium (+) Sulfate (-) CaSO4 and never sulfate calcium TRANSITION METALS can form more than one type of ion roman numeral must be included to indicate oxidation state of metal Iron (II) sulfate or Iron (III) sulfate (because they have more than one common charge -ic is higher oxidation state -ous is lower oxidation state MONATOMIC IONS -ide ending (for anions) (cations are first and names are unchanged) LiF -> Lithium Flouride Sulfur -> sulfide ion Hydorgen -> Hydride Chlorine -> Chloride REMEMBER elements combine via electrons (therefore the number of bonds is determined by the number of electrons either valence or charge the charge of a compound is ALWAYS 0 or neutral (if not then would interact until 0) Fe+3 and O-2 when in compound, charge is 0 Fe2O3 +6 and -6 = 0 ACIDS POLYATOMIC ACIDS -ate becomes -ic acid -ite becomes -ous acid nitrate -> nitric acid (HNO3) nitrite -> nitrous acid (HNO2) SINGLE ATOMIC ACIDS use -ic and HYDRO prefix HBr is Hydrobromic acid HF is Hydrofluoric acid BINARY COMPOUNDS for any two elements name the most metallic or the largest in size first use poly prefixes (or transition roman numerals) mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 Cu2S is Copper (1) Sulfide CrCl3 is Chromium (III) chloride HgSO4 is Mercury (II) Sulfate Fe2(CrO4)3 is Iron (III) Chromate https://www.youtube.com/watch?v=pPihneRSQec

Aufbau Principle (order of filling orbitals from low energy to high)

http://www.chemguide.co.uk/atoms/properties/atomorbs.html aufbau= german for building up or construction electrons fill low energy orbitals (closer to nucleus) before filling higher energy ones energy level 1: 1s energy level 2 2s 2p energy level 3: 3s 3p 3d energy level 4: 4s 4p 4d 4f HOWEVER, 4s is lower energy than 3d so 4s fills before 3d and then 4p fills after 3d (meaning 4p is higher energy) and will fill 6s before filling 4f (look at periodic table nd go by period to see when begin filling energy levels THE IMPORTANT JUNCTURES ARE 4S TO 3D starting at period 4 AND THEN 6S TO 4F TO 5D starting at period 6 S and P are always on same level the principal quantum number are APPROXIMATIONS of energy levels and as shown by d and f can have high energy What about when orbital has same energy? answer with Hund's Rule

Law of Mass Action

http://www.chemguide.co.uk/physical/equilibmenu.html law of mass action: RATE of reaction is proportional to masses of reacting substances (the more substance = faster reaction) Keq = [products]^x / [reactants]^y equilibrium constant where x and y are the coefficients of balanced equation (why is x and y to the power and not multiplied? remember that concentration: molarity is mole/liter if I need to find 8 of these molecules together at one time so molarity multiplies itself 8 times) rate is therefore the probability of finding 8 A molecules AND 3 B molecules at the same place at the same time. The best way to approximate this is to use concentration PURE LIQUIDS and SOLIDS are NEVER INCLUDED How does each affect equilibrium and equilibrium constant: the position of equilibrium moves to keep equilibrium constant constant ADDITION OF CATALYST? on equilibrium catalyst speeds up BOTH forward and backward reactions by exactly the same amount imagine transition state (Ea requirement is lowered for both forward and backward rates) dynamic equilibrium occurs when forward and backward rate are equal, equilibrium point will not shift. but if create situation where forward and backward rate are not equal (changing concentration INCREASE TEMP? doesn't affect mass or concentration at all (pressure does because based on moles) temp directly determines rate (how fast or slow molecules move and collide) the value of K rises or falls depending on endothermic or exothermic reaction imagine temp as factor in numerator or denominator, endothermic(numerator) and exothermic(denominator) increasing temp for endotherm increases rate constant increasing temp for exothermic decreases rate constant LOWERING EA? same as catalyst STABILIZING TRANSITION STATE? same as catalyst ADDITION OF REACTANTS OR PRODUCTS? equilibrium constant isn't changed by changing concentration position of equilibrium changes according to Le Chat favoring an increase in what was decreased and a decrease in what was increased Kc = [C][D]/[A][B]^2 changing C would change numerator ratio to denominator, so what happens, Kc is constant but equilibrium point will shift causing a increase in A and B and decrease in C and D IT IS BECAUSE KC IS CONSTANT THAT LE CHATELIER'S PRINCIPLE WORKS TO COUNTERACT ANY CHANGE likewise changing pressure of a system is like changing concentration (because pressure comes from number of moles) instead of using Kc use Kp and only consider gas molecules (again if same number of moles on both sides then changing pressure does nothing to equilibrium, because equilibrium can't shift to left or right to increase or decrease as both directions result in same no change, but when different number of gas moles then can favor one side or another to increase or decrease pressure Kp = Pc*Pd/Pa*Pb^2 where mole fraction*total pressure Kp = Xc*Xd/Xa*Xb^2*P Pb^2 becomes Xb^2 * P^2 by having 2 moles while all else has 1 mole because bottom has more moles pressure of system is in bottom like a concentration

Understanding Reaction Rates of Equilibrium

http://www.chemguide.co.uk/physical/equilibria/introduction.html#top A + B <-> C + D if we start with A and B and no C and D, at beginning we have max A and B so forward reaction is at its fastest as A and B react their concentrations fall, so less likely to collide and react so rate of reaction falls with time concentration of C and D increase so they start to collide and react forward rate decreases while backward rate increases until the reaction rates meet and become equal A and B will be converting into C and D at exactly the same rate as C and D converts to A and B, any further disruptions will simply find the rates seeking the same equilibrium position again a catalyst speeds up both the forward and reverse reactions by exactly the same amount, so equilibrium position would never change it would just arrive at equilibrium position faster

EMP to understand light and electrons better

http://www.chemistryland.com/CHM151W/07-Atomic%20Structure/Spectra/ModernAtom151.html wavelength: distance between one peak to another peak (of one cycle as in meters/cycle) frequency: how many waves or cycles per second (cycles/second) WAVELENGTH*FREQUENCY = SPEED OF LIGHT Av=c where c is a constant notice units m/cycle * cycle/s = m/s (the speed of light) wavelength is typically in nanometers (nm where n = 10^-9) MAX PLANCK studied relationships between temperature, color (frequency), and energy from a material as it absorbs and emits light previous theory was that high heat (energy) would produce more high frequencies than low but this was wrong so Planck assumed that higher frequency needed more energy thus reducing chances to be created so Planck created his famous equation E=hv h converts frequency into energy h= J*s and v = cycle/s also believed that energy increased in increments (quanta rather than continuous) Planck found out that the color emitted identifies the temperature (energy output) which is why we say the yellow in fire is hotter than red PLANCK SUCCESSFULLY RELATED LIGHT TO ENERGY VIA FREQUENCY Photoelectric effect since light is energy it could cause electrons to leave plate and generate a current Belief was that energy accumulated so visible light continuously shining would eventually eject electrons but that never happened (voltage too low) however if they used UV light, that ejected electrons and a current was generated. Why did UV light work by not visible? Einstein figured it out using Planck's work (E=hv) and proposed that light was not a continuous wave but a packet or particle of energy (light as particle photons) discovering the particle-wave duality of light and electrons energy could only transfer to an e- by being hit by one photon of light just as one particle hits another particle transferring energy with E=hv knew that higher frequency means more energy from photons so only when the photon energy was greater than binding energy of electron to plate did the photon knock off the electron LIGHT USED TO BE THOUGHT OF AS CONTINUOUS WAVE WITH ENERGY SPREAD OVER ENTIRE BEAM, EINSTEIN SHOWED HOW LIGHT SHOULD BE THOUGHT OF AS PACKETS OF ENERGY OR PARTICLES OF LIGHT (THE UNIVERSE AND EVERYTHING IS NOT CONTINUOUS BUT PACKETS THAT COMBINE TO GIVE ILLUSION OF SMOOTHNESS) E=hv the energy refers to a photon of light a packet of light as Planck thought but never argued for. RYDBERG why did hydrogen ONLY produce specific wavelengths of light? he didn't figure it out the why but came up with a formula that relates distance away from nucleus (energy levels) with the wavelength produced when changing energy levels discovered that wavelengths can only be changed in increments, and if wavelengths then frequency changes in increments, so does Energy, if Energy then so do electrons BOHR thoerized that the quantized energy that Planck suggested, Einstein proposed and Rydberg calculated could be the reason that certain frequencies of light were seen coming from hydrogen, that it's electron could only occupy certain energy levels within the atom and that light equaled the difference in the levels, and could cause electron to jump to higher level, when e- fell back down it would then emit the same frequency of light it had absorbed electrons were now viewed as orbits around nucleus where each orbit could only be at a specified distance from nucleus representing distinct energy levels creating principle quantum numbers BROGLIE "if waves could behave like particles (light as photons), can particles behave like waves (electrons)? came up with an equation relating mass of particle to wavelength planck's constant J*s J= kg*m^2/s^2 multiplying s and dividing by kg*m/s leaves m (which is wavelength) wavelength = plancks' constant / (mass*velocity) de Broglie's atom treats e- more as waves while bohr treated only as particles, but both maintain that energy levels are incremental and quantum with each electron added, they found a new position or shape that maximized distance from each other QUANTUM NUMBERS n determines the distance from the nucleus (represented by period) n=1 only s n=2 s,p n=3 s,p,d n=4 s,p,d,f l determines the shape where electrons are 90% of time (0=s=spherical 1=p=dumbell 2=d=?? 3=f=???) m tells orientation (axis) s= 0 p= -1,0,1 d= -2,-1,0,1,2 f= -3,-2,-1,0,1,2,3

Atomic Structure

http://www.docbrown.info/page04/4_71atom.htm atoms are smallest particle of an element or substance that can't be further split without removing properties Dalton model held that atom was smallest possible particle and the way they produced elements was by combining in different proportions to produce compounds we know But late 19th early 20th had atom experiments that showed sub particles (neutrons protons electrons) center of atom is nucleus with protons and neutrons and rest of empty space is occupied by negative electrons held by attraction to positive nucleus e- have relatively no mass compared to nucleus (1/2000 per nucleon) but occupy most the volume and determine the size of e- atoms are neutral because the charged particles cancel out, ions are always charged electronic structure of atoms determines chemical capabilities characteristics proton number shows as bottom subscript while mass number shows as top superscript isotopes have same chemical property (electrical arrangement) but may have different physical properties: heavier isotopes have greater boiling point and densities isotopes does NOT mean radioactive (unstable will break down) there are stable isotopes that exist in nature to find weight of an element consider all the isotopes and their relative abundance and avg them together for a representative number or atomic mass ELECTRONIC CONFIGURATION determines size/radius lowest energy filled first 1st shell: s (2 electrons) 2nd shell: s and px py pz (8 electrons) 3rd shell: s and px py pz highest stability is reached when outer level of e- is full (He has 2 e- or noble gas with 8 e- (NOTE NOBLE GASES ARE GROUP 0 not group 8) the most reactive elements are one e- away from a full outer shell metals (left) lose e- to acheive noble gas while nonmetals (right) gain e-

Periodic Trends

https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorganic_Chemistry)/Descriptive_Chemistry/Periodic_Trends_of_Elemental_Properties/Periodic_Trends Atomic Radius: half the distance between covalently bonded nuclei (of same atoms) (can't see the boundaries of e- cloud) ATOMIC RADIUS DECREASES to RIGHT (more protons less shielding e-) INCREASES DOWN (adding another shell level) (for ions cations are smaller because have less e- repulsion and more proton attraction, while anions are larger because same proton number but more electrons meaning more repulsion) within a period or family of elements, all electrons are added to the same shell. However, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. This means that the nucleus attracts the electrons more strongly, pulling the atom's shell closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases. ELECTRONEGATIVITY: atom's ability to attract and bind electrons uses Pauling scale (qualitive) nonmetals want to attract and bind e- (high electronegative) metals want to give away (low electronegative) the more likely atom is to gain e- the more likely it will pull e- towards itself small size = more proton power=more electronegative large size = less proton power= less electronegative ELECTRON AFFINITY: ability of atom to ACCEPT electron (quantitative unlike electronegativity which is qualitative) measure of energy change when e- is added to neutral gas atom (ABILITY TO FORM AN ANION) negative net energy equals lower energy = more stability the closer nucleus is to valence= more likely to attract e- to valance ELECTRON AFFINITY DECREASES WITH HIGHER SIZE INCREASES WITH SMALLER SIZE INCREASES to RIGHT DECREASES DOWN determined by proton force which is determined by distance metals have low EA (want to give away not accept) while nonmetals have high EA (want to accept) (Noble gases are exception don't want to add or remove electron) IONIZATION ENERGY: energy needed to REMOVE electron from GAS state (does not work in solid or liquid) (ABILITY TO FORM A CATION) \http://www.chemguide.co.uk/atoms/properties/ies.html IE IS MEASURE OF ENERGY NEEDED TO MOVE ELECTRON TO HIGHER ENERGY LEVEL (from n=3 to n=4) high energy = hard to remove , low energy= easy to remove (more and more energy is needed to remove successive electrons less repulsion, e-s are closer to nucleus with less e- repulsion but same number of protons) the closer the e- to nucleus = the stronger the proton force = the more energy it takes to remove e- from atom small radius means more energy, large radius means less energy metals like to lose electron (become more stable) non metals don't like to lose an electron and are smaller in general IE INCREASES TO RIGHT (smaller atoms) DECREASES DOWN (larger atoms) the size of atom decreases with more proton attraction adding a proton across period increases Zeff but principal quantum number remains the same Metallic character: metals like to lose electrons so metallic character is also ability to lose e- and is based on size the stronger the proton attraction, less likely to give off e- so less metallic character the larger the atom the greater the metallic character MELTING POINT: is the amount of energy required to break bond to change solid phase to liquid phase. stronger net bonds have higher melting points metals generally have high melting points while nonmetals mostly have low melting points (BUT Carbon has the highest boiling point of all elements followed by Boron) SIZE MATTERS periodic trends largely depend on the atomic radius smaller atoms have valence electrons closer to nucleus Coulomb's Law: F=kqq/r^2 the greater force on valance electrons determines all the other properties closer to nucleus= stronger force = more tightly held closer to nucleus = stronger force= more likely to attract electrons (electronegativity)

Molecular Orbital Theory and Bonding and Antibonding

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Chemical_Bonding/Molecular_Orbital_Theory/Pictorial_Molecular_Orbital_Theory Molecular Orbital Theory by Mullian incorporates the wave like characteristics of electrons and therefore allows more accurate predictions about shape, magnetism, and bond order than other models that consider electrons only as particles atoms make bonds by sharing electrons the exact position is impossible to calculate, but can calculate the probability which is used to predict energy and spatial distribution of the atomic orbitals when atomic orbitals combine (from two different atoms) they form molecular orbitals (if start with two atomic then have two molecular orbitals)(total number of molecular orbitals=total number of atomic orbitals) bonding orbitals are formed by in phase combinations of atomic orbitals that increase electron density between atoms resulting in lower energy than atomic orbitals (stable) antibonding orbitals are formed by out-of-phase combinations of atomic orbitals that pull electron density away from between atoms causing instability meaning energy is higher than atomic orbitals (key is where is e- density focused: between or away) in phase is like constructive wave interference increasing e- density between atoms causes extra shielding between nuclear repulsion making positive nucleuses less likely to repel and come together out of phase is like destructive interference where electron density is pulled away from between two atoms so they experience less shielding and stronger nuclear repulsion SIGMA BONDS sigma bonds form by overlap between electron clouds, where there is overlap there is an increased electron density resulting in increased negative charge. The increase in negative charge causes nuclei to be drawn closer together antibonds remove electron density causing no overlap so that close positive nucleuses repel PI BONDS pi bonds form by a side to side overlap (density above and below axis) p orbitals (after 1 is used to make sigma bond) have 2 orbitals at 90 deg from sigma that can overlap side to side and form 2 pi bonds (notice that since overlap is not directly between the two nucleases, the amount of shielding or reducing the positive like charges is less than a sigma bond (a sigma bond is stronger than a pi bond) for the first Z< or =7 pi molecular bonds are filled before sigma molecular bonds (up to Nitrogen starting with Oxygen, sigma bonding is filled before pi bonding, BUT sigma antibonding is still higher than pi antibonding BOND ORDER if antibond e- = bond e- then molecule is unstable and would not remain bonded Bond Order =1/2(bond electrons - antibond electrons) if bond>antibond then molecule is stable DIAMAGNETIC: no unpaired electrons in orbital (two or none in every orbital) PARAMAGNETIC: unpaired electrons in orbital (one in an orbital)

Practice of trends

https://ptable.com/ use table pick two random elements predict relative radius, electronegativity, ionization energy, electron affinity electron affinity and electronegativity represent same property: ability to attract electrons BUT electronegativity is qualitative using the Pauling scale of comparison electron affinity is quantitative measure of the energy release (negative) when an electron is added to gas phase Ionization energy is quantitative measure of energy needed to remove an electron

Orbitals and electron configuration

https://www.khanacademy.org/science/biology/chemistry--of-life/electron-shells-and-orbitals/v/more-on-orbitals-and-electron-configuration s = spherical (1 subshell) p = dumbbell (3 subshells) d = (5 subshells) electron configuration via periodic table group or column (if you can see it you can reason through it first 2 groups are s last 6 groups are p for neutral atoms, protons equals number of electrons the shapes that electron cloud takes is to minimize the repulsion from electrons

Balancing Reactions

https://www.khanacademy.org/science/chemistry/chemical-reactions-stoichiome/limiting-reagent-stoichiometry/v/stoichiometry-limiting-reagent 1) Carbons 2) Hydrogens 3) Oxygens 4) remaining 5) fractions (in x/2, the /2 makes O2 an O so x is what is needed) ex 7O and O2 7O= 7/2 O2 5O and O2 5O = 5/2 O2 32O = 32/2 O2 32O = 32/3 O3 6) after finishing the rest multiply by the bottom to get whole number moles the MOST COMMON ERROR IS FAILURE TO FULLY MULTIPLY BY COEFFICIENT 7) DOUBLE CHECK, number of atoms on each side are equal CHARGES ALSO SHOULD BALANCE THE MCAT WILL GIVE UNBALANCED REACTIONS https://www.thoughtco.com/balancing-chemical-equations-introduction-602380 (go to "WORKSHEETS FOR PRACTICING BALANCED EQUATIONS) Methane combustion CH4 + 2O2 --> 2H2O + CO2 Ethane combustion 2C2H6 + 7O2 --> 6H2O + 4CO2 Propanol combustion 2C3H8O + 9O2 --> 8H2O + 6CO2

Rutherford's exp

https://www.youtube.com/watch?v=5pZj0u_XMbc considering Thompson's plum pudding model of atom where charges were equally distributed they would shoot alpha particles (two protons+two neutrons) through a thin gold foil to see how (angles) the particles would scatter after colliding with atoms most particles pass through undeflected, but the surprising thing to experimenters was that a few alpha particles were deflected so strongly (greater than 90 deg or even a full 180) meaning alpha particles directly collided with something much more massive than alpha particles yet so small that only few alpha particles experience it hence nucleus is small not spread throughout entire atom but most of atom is empty space

What holds nucleus together?

https://www.youtube.com/watch?v=mpDDQ4uEH6M r like charges repel so why doesn't positive charges in nucleus repel and fall apart? because of a stronger counter force called STRONG NUCLEAR FORCE that only works at a very small range (between both protons and neutrons) (that's why larger nuclei tend to be unstable because more likely to have distances that exceed the range there are four basic forces in nature and the strong force is one of them gravity, electromagnetic force, strong nuclear force, and weak nuclear force) strong nuclear force is actually the strongest of the four but has the shortest range of action (if not stronger than force of electrostatic repulsion, would never have atoms form in order to combine two protons, must be moving fast or under a lot of pressure to overcome electrostatic force (like vs. like) this is also why neutrons are helpful, by not having charge they don't contribute electrostatic instability themselves but can also slightly separate protons to weaken charge repulsion while keeping strong force active strong force works by having a particle exchange between two close particles called a meson that bounces between

Le Chatelier's Principle

if reaction is already at equilibrium adding or taking will cause reaction to be suddenly AWAY from equilibrium and reaction will proceed to relieve the stress and RETURN to equilibrium Equilibrium point did not change (unless changed temp) because Keq did not move or change (DO NOT SAY THAT EQUILIBRIUM SHIFTS, SAY REACTION SHIFTS, K is constant but Q can be changed) ALL LE CHAT INVOLVES IS CHANGING Q, NEVER CHANGES K unless temperature has changed (enthalpy (equilibrium) and rate) Keq doesn't change because we add or take concentration or change the pressure, Keq stays constant and the concentrations of products and reactants adjust to match original Keq equilibrium is an intrinsic law of nature, at a given temp, for any specified reactants and products, the energy difference between them is FIXED (entropy is fixed (unless temp changes which measure of enthalpy connection to Gibbs law))

Ionic Radii

important to understand that cations LOSE electrons and anions GAIN electrons this creates two different trends for ionic radii for cations losing e- that means radius gets smaller as effective proton force increases (the further away neutral is from octet config to left the smaller the ionic radius will be) for anions gaining e- means radius gets larger with more e- repulsion (the further away from octet config the greater the ionic radius will be) on periodic table the trend of going right on period lowers radius still holds but when switching metal cations to nonmetal anions (sudden huge ionic radius that gets smaller (because less protons and more electrons means larger radius while more protons and same electrons means smaller radius)

Hund's Rule

in same energy orbital (like px py pz), electrons will minimize repulsion by only adding singly as far as possible and then double up in same orbital (max of 2) when absolutely necessary http://www.chemguide.co.uk/atoms/properties/atomorbs.html

Covalent vs. Ionic

ionic bond is formed by attraction of opposite charge (ONLY METAL AND NON METAL FORM IONIC) (NM and NM = covalent and M and M = covalent) losing or gaining an e- forms an ion positive charged ions are called CATIONS after being attracted to negative charged CATHODE in electric field negative charged ions are ANIONS after being attracted to positive charged ANODE in electric field IONIC BONDING: transfer of electron(s) between two dissimilar atoms (because difference in electronegativity) COVALENT BONDING: when electrons are shared between two similar atoms of similar electronegativity COORDINATE COVALENT: where both electrons shared in bond are donated from a single atom (that atom therefore MUST have a lone pair of e-s) non metal ionic compounds typically use NH4+ (only common polyatomic ion with a plus charge (most are metals with negative)

Second Quantum Number (l)

l = the azimuthal quantum number or the angular momentum quantum number gives subshell or orbital with values of 0,1,2,3 0=s (spherical) 1=p (dumbell) (cool thing is it shows how e- has to jump between lobes) 2=d 3=f meaning we know its shape

Acid-Base

like double displacement reactions if define acid and base in terms of H and OH then combining acid and base yields water and salt HA + BOH -> BA + H2O

Beta Decay

lose an electron, neutron becomes proton (minus charge leaves, positive charge remains) in nucleus, a neutron is changed into a proton by losing an electron 1 NEUTRON becomes 1 PROTON mass doesn't change, but identity of atom changes (if losing an electron in nucleus then have to gain proton to keep charge conserved) (if minus leaves then what remains is positive) but atom does atomic number increases by 1? NO proton+neutron outside, an electron is ejected (charges balanced) (when neutron = proton + electron and electron leaves, left with proton) opposite of electron capture e- leaves nucleus neutron becomes proton

Moles of Oxygen needed for Combustion?

may be asked to predict the species that will require the most oxygen to combust is based on balanced equation, but need to be able to quickly recognize which would need more or less THE MORE CARBON, THE MORE OXYGEN NEEDED TO BURN IT IF ALREADY OXYGEN IN MOLECULE, LESS OXYGEN IS NEEDED use ranking system (does not give moles needed, again would have to write balanced equation for that) ADD 1 for each CARBON SUBTRACT 0.5 for each OXYGEN (that is within molecule) compare propane, propanol, and propanoic acid all have same amount of carbons (3) propanol has 1 O while acid has 2 O propane requires most Oxygen to combust, while propanoic acid requires the least therefore propanoic will combust first and propane last

metals and nonmetals

metals 1-3 electrons in outer shell (easily lose them to be stable) form oxides that are BASIC (donate electrons) reducing agents (cause reduction= donate e-) low electronegativity (want to give e- not take them) nonmetals 4-8 electrons in outer shell (easily take them to fill shell and be stable) form oxides that are ACIDIC (take electrons) oxidizing agents (cause oxidation= take e-) high electronegativites (the better to take e-) http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html physical props metals good conductors malleable, ductile (beaten or stretched) luster opaque as thin sheet solid at room temp (higher melting point) nonmetals poor conductors brittle no luster transparent as thin sheet solids, liquids, or gases at room temp (tend to have low melting points)

Third Quantum Number (ml)

ml= magnetic quantum number gives orbital orientation (as well as possible number of orbitals) DESIGNATES THE ORIENTATION OF SUBSHELL WHERE AN ELECTRON IS MOST LIKELY TO BE FOUND based on l value 0,1,2,3 and includes - and + to denote how many subshells l= n-1 (because start with 0 while n starts with 1) l=0 (s) ml = 0 = 1 (s has 1 subshell) l= 1 (p) ml = -1,0,1 (p has 3 subshells px py pz in 3 orientations and an electron can be in any one of them) (4 cumulative orbitals) l=2 (d) ml = -2, -1, 0, 1, 2 (d has 5 subshells) (9 cumulative orbitals) l=3 (f) ml = -3,-2,-1,0,1,2,3 (f has 7 subshells) (16 cumulative orbitals) notice how each successive l gives two new subshells or orbitals and each can have two electrons

Decomposition

molecule breaks down into simpler 2H2O2-> 2H2O + O2

How does increasing [reactants], [products], [catalyst], Ea, energy of transition state, energy of reactants, and temp AFFECT REACTION RATE

more reactants = more chances to react = faster rate (as long as reactant is apart of rate law) more products = doesn't affect rate at all only affects reaction direction (thermodynamic quality) (kinetics is studied usually at the beginning when there is no product and we want to see how fast something occurs also there are no products in RATE LAW more catalyst = would lower activation energy for more molecules, BUT there is a limit, if number of catalysts start to exceed number of reactants then reactants act like a limiting reagent and adding excess catalyst causes no change to rate : graph starts strong and curves to a horizontal more Ea= higher hurdle for molecules to jump over slowing rate energy of transition= same as Ea more energy of reactants brings more molecules closer over Ea barrier speeding reaction more temp= more energy of reactants (higher ability to overcome activation energy (AFFECT OF TEMP ON Ea IS MUCH STRONGER THAN TEMP EFFECT ON COLLISIONS hence Max-Boltzmann) because just bouncing against each other is not enough for reaction both molecules need enough energy to overcome Ea break and make new bonds more surface area = more chances for reaction (giant ice cube vs lots of small ones) remember that this is probability, at low temp there may be molecules that can have energy to combine its just few and far inbetween https://www.chem.tamu.edu/class/fyp/stone/tutorialnotefiles/kinetics/factors.htm

Elements and Atoms

most basic unit is the atom beyond which breaking down ruins the properties proton defines element has mass and positive neutron in nucleus have mass electrons no relative mass have negative charge around nucleus and are bound by positive charge of protons charge is determined by the number of electrons, protons don't change but are in nucleus, electrons surround nucleus and can be added or taken and will determine how atoms react

Hydrogen Bonding

moving down a group causes increase in boiling point because increased size means more electron dispersion (even with Hydrogen in groups like 4) but something very unexpected occurs when graphing boiling points of groups 5 6 7 with Hydrogen H2O, HF, NH3 have very very high B.Ps relative to rest of group (B.P. decreases towards nonmetals holds (smaller atoms have less e- dispersion holds) O, F, N when H is attached DIRECTLY to the most electronegative elements (causing H to acquire large amount of positive charge) NOTICE how each of molecules above has a lone pair of electrons to have H bonding need very electronegative element with H and a lone pair (e- rich to attract positive rich H) to make intermolecular force the intermolecular force with Hydrogen is more powerful than size and its related to electronegativity because moving down group (where there is weakened electronegativity) we don't see the benefit of H bonding O,F,N in first period has small size so lone pair is smaller volume meaning a higher density of negative charge, with larger size the electrons are more diffuse (greater for london forces not as great for H bonding) and electron cloud is not as dense and not as attractive to positive things REMEMBER THAT A COVALENT BOND IS significantly STRONGER THAN AN INTERMOLECULAR FORCE still the number of intermolecular bonds gives strength with hydrogen bonding, consider the number of lone pairs to H atoms (bonded to O,F,N) H2O has 2 l.p. and 2 H-O while HF is weaker (3 l.p. but 1 H) KEEP IN MIND THE NUMBER OF H BONDS MAY BE DETERMINED NOT BY L.P. AND H BUT SOLELY BY H (EVEN THOUGH ITS BETTER TO THINK OF BOTH) H bonding determines physical properties when size is similar and OH is stronger than NH with more intermolecular strength, the more heat it takes to break, the higher the boiling point ethanol CH3CH2OH and methoxymethane CH3OCH3 have same size, same number of electrons and same dispersion and dipole dipole forces, yet because of OH bond methoxymethane has b.p. -24.8 ethanol has b.p +78.5 H bonding exists IN ADDITION to Van Der Waals (dispersion and dipole) pentane and butan-1-ol and 2-methylpropan-1-ol contain same number of electrons (count by the nonmetal atoms, C and O) can tell the ols will have much higher b.p. than pentane 1 ol is branched and the other is straight chain, which has higher b.p.? same amount of H bonding. BRANCHING REDUCES VAN DER WAAL INTERACTIONS (allows less dispersion) http://www.chemguide.co.uk/atoms/bonding/hbond.html#top

Fourth Quantum Number (ms)

ms= electron spin quantum number gives the spin +1/2 or -1/2 (up or down arrow since only two electrons can inhabit same orbital

First Quantum Number (n)

n = the principle quantum number identifies the shell and represents the approximate relative energy of electrons in that shell 1 = closest to nucleus higher n = further away and more energy 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f

Pauli Exclusion Principle

no two electrons can have same four quantum numbers, an orbital can only contain a max of two electrons so spin will either be up or down

How Bohr's model is wrong and right

not a planetary model, but orbital shape of probability that represent high chance (90%) of finding electron don't confuse orbitals with shells (first shell and orbital is filled with 2 e- but next orbital contains 8 e- and two shells. there is an energy difference between s and p shell (higher = further away in distance) yet Bohr model doesn't show this protons and neutrons are same size electrons are really small making orbital shells mainly empty space if a dot was the nucleus the dorm room would be the electron clouds as a point towards Rutherford experiment Bohr is very useful for discussing energy levels and jumping when receiving the specified quanta of energy and release energy as light electrons were discovered as having dual nature of wave and particle behaving like light electrons DO NOT orbit in a ring, electrons are contained in s,p,d,f orbitals with different shapes based on electron repulsion (not boundaries but probabilities of where e- is likely to be s 1 shell 2 e- p 3 shells 6 e- (8 total) d 5 shells 10 e- (18 total) f 7 shells 14 e- (32 total)

significant figures

past a decimal point all 0's mentioned after a number are significant 4032.090 (that last 0 is significant) likewise 4032.0900 the last two 0s are significant when adding or subtracting, goes to shortest decimal place (minimize to right of decimal .01 and 1 =1 ) or whole number (minimize to the left of decimal 45001 - 56.355 -78.44 = 44866 (only to 1's position) when multiplying or dividing keep only the lowest number of significant figures 98.1*0.03= 3 (1 s.f) 6.90/2.8952 = 2.38 (3 s.f.) a conversion that is EXACT will have an INFINITE number of significant

Heisenberg uncertainty principle

position and momentum cannot be simultaneously measured with precision the more we know about either position or momentum the less we know about the other (NOT A MEASURE OF QUALITY OR INACCURACY OF INSTRUMENTS) it comes from wave and particle properties inherent in quantum physics as size becomes more atomic it becomes less valid to assume a hard sphere, the smaller the dimension, the more wave like it becomes when considering a single wave, the momentum is precise but the position is unknown spread throughout the entire wave if considering several waves of different wavelength, the interference pattern acts to localize the waves to a more specific position (wider spread of wavelength means smaller range of x) but the momentum is now uncertain thanks to many different waves considered so we shift from trying to find absolute position and direction of electron to probability of location based on waveform equations

Bohr Model of atom

purpose to describe how electrons have stable ORBITS around nucleus Rutherford model had unstable motion of electrons: according to classical mechanics any charged particle on a curved path would continuously spiral into the nucleus and constantly lose energy and radiation eventually to collapse and stop existing WHAT BOHR PROVIDED required that electrons move in orbits of FIXED size and energy and the energy depends on size of orbit and distance from nucleus radiation and movement only occur when electron receives or gives out fixed energy and JUMPS into next orbit energy of electron is lower the closer to the nucleus and higher away from the nucleus at the closest orbital electron will be most stable HOW HE GOT THERE understood classical mechanics alone CANNOT explain atom stability that the equation would require length which all previous models neglect (only focusing on charge and mass) Planck's constant has dimensions when combined with mass and charge of electron produces length leading Bohr to use it to understand atoms P's constant explains the light radiation emitted from heated bodies and that energy could only be emitted or absorbed in discrete amounts Planck came up with quanta: how much (previous thought was comparable light energy is produced at all frequencies but that implied energy radiated is infinite) his constant claimed radiation only occurs in quantum amounts of energy and if radiant energy is less than quantum, the amount of light in that frequency would be reduced correctly describing radiation constant itself has dimensions of action: units of energy*time, units momentum*length, or units of angular momentum h=6.6*10^34 joule seconds Bohr took this constant to make an accurate formula for energy levels of hydrogen atom. applied Planck to electrons: angular momentum of electron is quantized with discrete values and therefore electron orbits are FIXED in size and energy and electrons JUMP orbits by emitting or absorbing fixed energy ( we get quantum number for energy from the orbit) when absorbing energy, e- jumps away when e- jumps back it releases the same energy in the form of light with fixed quanta, energy emission and absorption is fixed as the difference between energy levels of orbits just like potential energy, the further away the more energy the difference in energy (distance) between the first and second level is the greatest and successively get smaller this is the equivalent of gravity and Coulomb where the closer the masses or charges are the stronger the force between them

Radioactive Decay and Half Life

radioactive decay is when unstable atoms change their chemical composition over time the mass and atomic number, and charge must be conserved across both sides of equation different types nucleus sometimes gains or loses electrons loses or gains protons and neutrons IMPORTANT NOTES: (for Beta Decay: loss e-, Electron Capture: gain of e-, Positron Emission = loss of positron) Beta decay involves either loss of electron from nucleus= neutron -> proton gain of electron into nucleus= proton -> neutron loss of positron from nucleus= there are two important relationships to make think of NEUTRONS as neutron = a proton + an electron (remove e- and neutron becomes proton) think of PROTONS as proton = neutron + a positron (remove positron and proton becomes neutron nuclear stability only unstable nuclei decay Strong nuclear force holds nuclei together (otherwise protons would repel each other) Neutrons help space protons out to weaken electrostatic repulsion small atoms tend to have equal numbers of protons and neutrons larger atoms tend to have more neutrons than protons (still having too many neutrons will make nucleus unstable) https://www.slideshare.net/Komperda/nuclear-decay-3533196

Radioactivity

radioactivity comes from tug of war between strong nuclear force (stronger but less range) and electromagnetic (weaker but broad range) ALPHA particles: have two protons and two neutrons (Helium with mass of 4 and Z=2) because of mass and charge, alpha particles have very narrow range BETA: when a neutron gives off a quark (like it loses an electron -like particle and neutron becomes proton) http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/nucnot.html

Rate Laws

rate is determined by how much reactant is consumed (not concerned with how much product made that is more an equilibrium thing not a rate) only consider the first few seconds of the reaction, where there is a high concentration of reactants and any catalysts rate is a measure of disappearance of reactant M/s (likely to decrease as concentration decreases but the rate of change for the rate depends on order of reaction) RATE LAW IS VERY DIFFERENT TO EQUILIBRIUM Equilibrium considers concentration of both reactants and products and the powers come from stochiometric coefficient of moles rate law ONLY considers concentration of reactants and powers are a measure of how change in concentration determines change in rate order is determined experimentally (except when reaction is ELEMENTARY: mole coefficients = rate orders)(for MCAT always assume NOT elementary, they probably want to see if know difference between rate and equilibrium) rate powers determine the reaction order Equilibrium = Keq = [C]^c*[D]^d/[A]^a*[B]^b Rate = k[A]^s * [B]^t k is rate constant that depends on temperature and Activation energy (Arrhenius Equation)

Collisions cause reactions

reactants must collide with enough energy to overcome energy of activation reactants must have correct spatial orientation we measure rate by change in molarity (M=mol/L)(M/s) of reactants per second or simply concentration over time since rate of reaction, decrease of reactants means creating products so change will be negative (however rates are not expressed as negatives so they usually have a negative sign to make rate positive) products will be forming so their rate M/s is positive important that rate is in terms of 1 mole so when A + 3B -> 2D [A]/t = [B]/3t = [D]/2t divide rate of B by 3 to get rate of 1 mole and not 3 (even though that is what the reaction would be)

Bond Length and Bond Energy

remember atoms are not ball and stick models but electron clouds bond length is determined by distance between nuclei Bond energy: the amount required to break bond, which is a measure of bond strength atoms only form new bonds because it results in lower energy the change in energy is released (to break a bond input energy, to make a bond is to release energy) misconception that the breaking of ATP produces energy, no the breaking of bonds actually requires energy, but forming the bonds of ADP results in much lower energy releasing the difference to be used, THE FORMATION OF ADP CAUSES RELEASE OF ENERGY NOT THE BREAKING OF ATP ENERGY IS ALWAYS REQUIRED TO BREAK A BOND. ENERGY IS ALWAYS RELEASED WHEN A BOND IS FORMED STABLE compounds HIGH high bond energies UNSTABLE compounds have LOW bond energies "high energy" doesn't mean high bond energy but the opposite, it means unstable and requires very little or no energy to break (whereas high bond energy requires a lot of energy to break) when bonds are formed they are lower in energy (that is why they form in the first place to go from high energy to low stable energy) bonds are a measure of stability low energy of molecule (high charge ions with greater charge form stronger bonds) imagine an energy diagram, remember how atoms join to form lower energy compounds, they appear low on graph, to get back to starting atoms, need to add energy raising the energy graph NOTE a compound with high energy is the opposite of high bond strength (high energy implies bonds are going to be broken to release energy, if bonds are broken that is weak bond strength) ATP or any compound that readily dissociates will have weak bond strength while very stable molecules like water (high b.p.) will have high bond energies WHEN BONDS ARE STRONG, THE ATOMS ARE CLOSER TOGETHER it takes more energy to physically push them apart (think of Potential Energy and relaxed position) when atoms are further apart, the weaker the attraction BOND DISSOCIATION ENERGY is similar to bond energy : amount of energy (MCAT treats same as bond energy) but to be specific, bond energy is avg of gas-phase bond dissociation energies of all bonds of that same type in that same molecule

electron configuration exceptions

remember that e-s will fill lower energy level first before higher level that is why 4s gets filled before 3d and why 6s gets filled before 4f BUT some situations make it more energetically favourable to take an e- from s and move to d or f a half or fully filled d orbital is more favorable (lower in energy) than a full s orbital and 1 less than half or fully filled d orbital http://www.chemguide.co.uk/atoms/properties/elstructs.html

Synthesis

simple compounds combine to make a more complex one making a sandwich is a complex reaction 2Na + Cl2 -> 2NaCl

Heat of Combustion

the amount of energy (heat) released when a molecule is combusted with Oxygen, where all covalent compounds are broken and reformed in a radical reaction delta H would be negative since releasing energy (exothermic) REACTANTS ARE HIGHER THAN PRODUCTS meaning the more energy/unstable the more release of energy CH3OH + O2 --> CO2 + 2H2O He=890 kJ/mol Carbon Dioxide and Water are very stable, heat of combustion represents the energy difference in energy (on coordinate use the height difference) unstable moleulces will have high heights indicating high energies is a measure of total energy of molecule (high energy=less stability) and USED IN BOMB CALORIMETER by measuring temp change units of energy/mass or energy/mole or energy/volume low energy molecules (most stable) are going to release low energy unstable molecules (high energy) are going to release high energy will low bond energy or high bond energy have higher heat of combustion? high bond energy means more stable (the molecule is low energy and snugly with partner) it is already at lowest point so would release very low energy low bond energy means atoms are unstable meaning high on an energy diagram, when they break, they release the energy they have K is LARGER than Na and will therefore have MORE METALLIC character (increased size means more delocalization = sea of e-) so Na will need higher concentration to match electric condosity to match KCl Li is SMALLER than Na and therefore LESS METALLIC than Na Na is stronger conductor so don't need as much to conduct the same amount of electricity

Work Function

the amount of energy needed to eject electron from outermost shell (valence shell) of a SOLID METAL Work = Force* distance it is energy which is a measure of how much distance is covered to eject electron like Ionization energy but difference is IE is used to eject e- from atoms in gas state while "work function" ejects e- from solid metal when an energy is added to eject e- less energy than work function and e- will not eject any more energy than work function and e- will eject and the excess energy will convert to the kinetic energy of now free electron IMPORTANT IF ENERGY ADDED IS EXACTLY EQUAL TO WORK FUNCTION WHAT WILL HAPPEN? well electron will be "technically free" but will not have any remaining to go into KE so will remain motionless meaning nothing has really happened Remember the photoelectric effect, phototube using light on metal plates (visible light didn't have enough energy but UV light does) to eject electrons and give them velocity to reach other plate KE= Energy added - work function KE= E - w and energy added (E=hf) = planck's constant * frequency which represents the energy of light or the energy of photon and frequency*wavelength = speed of light fA=c f=c/A frequency is cycles/second wavelength is meters/cycle speed is meters/second E=h(c/A) DOES NOT DEPEND ON INTENSITY (the number of photons emitted) OR AMPLITUDE BUT DOES DEPEND ON WAVELENGTH WHICH DETERMINES FREQUENCY OR ENERGY however if energy > work function then increasing the (intensity) number of particle interactions will increase the number of electrons ejected https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Map%3A_Physical_Chemistry_(McQuarrie_and_Simon)/01%3A_The_Dawn_of_the_Quantum_Theory/1.3%3A_Photoelectric_Effect_Explained_with_Quantum_Hypothesis https://www.youtube.com/watch?v=OCYyPdn_9PU

Effective nuclear charge (Zeff) reason for atomic radius

the net positive charge experienced by an electron Zeff= z-s z=number of protons s=shielding electrons (only on previous energy levels or if they are between e- and nucleus) (inner e- shield valence e- from nucleus) as atoms increase in size they experience more shielding by electrons before them the effective nuclear charge is therefore less than expected (when only considering proton effect) when moving to the right of period table, more protons are added but no shielding electrons are added (relatively same quantum level =period) so moving to right atomic radius gets smaller experiencing a higher effective nuclear charge when moving down group (changing period = changing quantum levels adding a new shell further away (more energy) creating more shielding electrons so e- don't feel as strong a pull (fun fact even when e-s are paired in same orbital, they experience repulsion from each other offsetting attraction from protons in nucleus) when going to next period element (the adding of proton really increases effective charge, but the added electron doesn't provide any additional shielding

Simple view of atomic structure

the subatomic particles proton mass of 1 and charge of +1 neutron mass of 1 and no charge electron mass of 1/1836 and charge of -1 (thanks to taking an avg weight, protons and neutrons don't have an exact weight of 1 because amu is based on carbon 12 scale so little higher than 1) CHARGE AND ELECTRIC FIELD in an electric field (created by a positive and negative charge plate) opposites will attract protons would deflect towards negative plate electrons would deflect towards positive plate (reason for why protons and electrons are attracted to each other: charge) neutrons have no charge so no reason to be attracted or repelled HOW MUCH ENERGY AND ELECTRIC FIELD remember that speed is a measure of energy and energy is a measure of speed if an electron and proton have same energy they will be deflected by the same amount just in opposite direction HOW MUCH SPEED AND ELECTRIC FIELD BUT notice if an electron and proton have the same speed they will not have equal deflection. the electron will be greatly deflected while the proton only moderately Why? because energy is KE=1/2 mv^2 and an electron has much much less mass than a proton less mass means lower energy, less energy means easier deflection same speed is very different to same energy because of different mass IT is the ENERGY that determines behavior (like in pressure) THE NUCLEUS protons and neutrons make nucleus and are called nucleons where all the mass of an atom resides (e- weigh very little) Atomic number= number of protons determine periodic properties Mass number=number protons+neutrons (also is the nucleon number) (to calculate neutrons take mass number and subtract atomic number) atomic number is always the smallest number ISOTOPES number of neutrons can vary thus changing the mass, but the chemical properties aren't changed at all (depends on electron numbers) the avg is weighted based on abundance in nature. can compare avg mass to isotopes to geusstimate which is likely more abundant THE ELECTRONS no of e- = no of protons when neutral (the charge indicates how many more electrons than protons (negative) arrangement e- always fill lowest possible energy level nearest to nucleus and further outward (there are arrangements where a half filled or fully filled d subshell takes precednece over a full s shell and partial d shell) determined by periodic table note: the group number determines outer shell e- arrangement (determines reactivity)

Theoretical and Percent Yield

theoretical: based on balanced equation (what is possible to get) actual: not all may react even though it is possible, plus some may get lost in transfer ACTUAL YIELD IS ALWAYS SMALLER THAN THEORETICAL Percent Yield: is a measure of how close actual got to theoretical possibility Percent yield = mass of product actual/mass theoretical IMPORTANT: YIELD IS A FUNCTION OF REACTANTS AND EQUILIBRIUM NOT rate Does providing a catalyst improve the yield? No, only changes how we fast we get to final yield without changing amount of yield Does adding reactants improve the yield? Yes the quantity produced is increased, but it DOESN'T change the percent yield DOES TAKING AWAY PRODUCT AS FORMED IMPROVE PERCENT YIELD? Yes, because force reaction in constant state of catch up that continually produces more product to reach back to equilibrium Le chatelier's Principle deals with equilibrium disruptions and how reactions will shift to go back to equilibrium removing product as they are formed shifts equilibrium into a constant state of "catch up" where the reaction continually produces more product in an attempt to reach equilbrium adding reactants also increases yield (NOT PERCENT, because increasing grams increases BOTH actual AND theoretical BUT adding reactants will ONLY work if adding more of the limiting reagent, if add more to excess reaction remains unchanged because don't have all reactants necessary for reaction

Collision Theory of Reaction Rates

to react must come into contact have to collide with enough energy to break bonds (overcome Ea) or they bounce away Ea comes from need to break bonds before making new ones (reactants to peak) (kinetic) energy released is a thermodynamic quality (reactant line to product line) endo means products are higher than reactants hence need to input energy exo means products are lower than reactants (release energy) TRANSITION STATE is at the top of activation energy (always higher than reactants and products, because it contains both the bonds of reactant (half formed) and bonds of product (half broken) not so much the bonds but the species together making everything unstable (at this top point reaction can proceed in either direction) Intermediates (lower than transition states) will be a dip in energy before and rise in energy will follow (2nd transition state) whichever transition state is highest is the slowest and will be rate determining step individual molecules can change energies all the time, but the avg for the whole will remain constant unless temp changes

Van der Waals Forces

weaker forms of INTERMOLECULAR interactions ALL INTERMOLECULAR ATTRACTIONS ARE KNOWN COLLECTIVELY AS VAN DER WAALS (INTERMOLECULAR FORCES DETERMINE SOLID, LIQUID, GAS AND HOW MUCH ENERGY TO TRANSITION BETWEEN intermolecular: attractions between one moleule and neighbor intramolecular: forces of attraction that hold an individual molecule together(covalent bonds apply) they are so similar Van der Waals dispersion forces: or London dispersion attractions are electrical and on avg a symmetrical molecule doesn't seem to produce polarized parts HOWEVER electrons are mobile and in one instant they may move to other parts of molecule, making temporary polarizations (even in noble gases) the partial charges then induce electrons to move away or closer causing induced dipole from neighbor atoms will therefore synchronize based on differences that occur instant to instant (stronger dipoles will determine syncrony) HOW SIZE AFFECTS STRENGTH OF BONDING increase in size means more space for electrons to move (plus extra electrons to move around) which means more possibilities/distances the electrons have therefore the LARGER the dispersion forces MORE SIZE = MORE e- DISPERSION = MORE van der Waals = HIGHER BOILING/MELTING POINT shape matters too (long and thin equal more dispersion than small and round) every molecule experiences dispersion fores electrons are not locked in ions experience permanent dipoles so stronger interactions meaning higher boiling and melting point LETS COMPARE SIZE TO ELECTRONEGATIVITY AND DIPOLE-DIPOLE IN INCREASING B.P. ethane(two methanes) fluoromethane are both same size yet because Fuorine is way more electronegative yet the boiling point increase is only 10 deg CHCl3 or CCl4 CCl4 has more electrons the extra Cl provides a larger size and larger dispersion forces even though net dipole-dipole

Alpha Decay

when a nucleus loses 2 protons and 2 neutrons (He nucleus mass of 4 and Z = 2) or when losing a mass of 4 and atomic number of 2 2 PROTONS AND 2 NEUTRONS ARE TAKEN AWAY atomic number decreases by 2 mass decreases by 4 He atom has no electrons (it is an ion) so no electrons are taken away! But it has become a -2 (losing protons so it quickly loses 2 electrons to environment) the He atom likewise is a +2 but quickly gains 2 electrons from environment and both become stable Gold has atomic number of 79 which under alpha decay becomes 77 and mass of 185 becoming 181 which is Iridium due to increased mass, alpha particles travel at 10% speed of light with low penetration, still if inhaled or ingested alpha particles do heavy damage to cells

Positron Emission

when a positron is emitted, (proton = neutron + positron, a PROTON becomes NEUTRON (when proton = positron and neutron and positron leaves, left with neutron) a positron has RELATIVELY no mass similar to electron and like an electron written as e with subscript but with +1 note some sources will label positron emission as a type of Beta decay (the MCAT however favors differentiating between positron and beta as in ALTIUS manual)

Oxidation-Reduction (Redox)

when the oxidation number of atoms change oxidation = loss of electrons resulting in positive oxidation state reduction = gain of electrons making negative oxidation state reducing agent = being oxidized (loses electrons to give) oxidizing agent = being reduced (takes electrons and gains) H2 + F2 -> 2HF H and F are originally neutral (no polarity electrons shared equally) when react, F is very electronegative taking electrons toward it Fe + CuSO4 -> FeSO4 + Cu reactants Fe starts with 0 Cu has +2 because SO4 is -2 products Fe: 2+ SO4: 2- Cu: 0 NOTICE how SO4 remains the same oxidation state therefore it does not contribute in redox reaction POLYATOMIC ATOMS GENERALLY DON'T BECOME OXIDIZED OR REDUCED Cu and Fe change Cu: +2 -> 0 (gain) Fe: 0 -> +2 (loss)