Chemistry 1

THINK OF PROTONS AS

protons = neutron+a positron

Pauli Exclusion Principles

the Pauli Exclusion Principles states that no two electrons can have the exact same four quantum numbers (i.e. occupy the exact same quantum state.) They can have up to three identical numbers, but then they must have opposite spins of +1/2 and -1/2.

Electron Affinity

the energy change when a neutral atom attracts an electron to *become an anion*.

Ionization Energy

the energy required to remove an electron from a neutral atom and form a cation - Recall that after an electron becomes excited, it can "relax" and return to its previous, lower energy level, releasing a photon in the process. This is what accounts for photon ejection, phosphorescence, fluorescence, etc. Because an atom has the highest Ionization Energy, it will require the greatest amount of energy to promote an electron to a higher energy level. *measured for lone atoms in a gaseous state*

Bond Energy (Covalent Bonds Only)

the energy stored in the bond. -This is also the amount of energy that will be required to break the bond. -Don't confuse this; stable compounds such as N2 have the highest bond energies. Unstable compounds, such as ATP, have LOW bond energies. *When something is said to be a "high energy" molecule that does NOT mean it has high bond energy. In fact, it means the very opposite. It is unstable and thus requires very little energy to dissociate the bond.*

dynamic equilibrium

A dynamic equilibrium occurs when you have a reversible reaction in a closed system. Nothing can be added to the system or taken away from it apart from energy. At equilibrium, the quantities of everything present in the mixture remain constant, although the reactions are still continuing. This is because the rates of the forward and the back reactions are equal. If you change the conditions in a way which changes the relative rates of the forward and back reactions you will change the position of equilibrium - in other words, change the proportions of the various substances present in the equilibrium mixture. This is explored in detail on other pages in this equilibrium section.

Mole

A mole is defined as Avogadro's number of anything. Just as a dozen is defined as 12 of anything, a mole is 6.022 x 10^23 of anything

Radioactive decay

*the process by which unstable atoms change their chemical composition over time*. -The nucleus sometimes loses or gains electrons, lose bundles of protons and neutrons called "alpha particles," or even transforms one subatomic particle into another.*

The nucleus of the Bohr Model of an Atom

-A nucleus is made of protons and neutrons held together by the residual strong force (i.e., the residual force left over from the strong nuclear force that binds quarks together to form individual nucleons. -Protons are positively charged, neutrons are neutral, and they are approximately the same size and mass. -Electrons are much, much smaller—roughly 1/2000 of the mass of a proton. -Because electrons are so small, the electron cloud is mostly dead space. -A good approximation of relative size would be to explain that if a student sat in the middle of their dorm room and put a pencil dot on a piece of paper, that dot could approximate the size of the nucleus and the size of the electron cloud would fill the entire room. *This might approximate the "average" atom. There is obviously a huge variance in size between hydrogen and francium.* Emphasize that because of how small electrons are compared to the size of the electron cloud, atoms are mostly empty space.

How does each of the following affect equilibrium: addition of a catalyst, increased temperature, lowering the Ea, stabilizing the transition state, addition of reactants/products?

-Addition of a catalyst impacts rate but does nothing to equilibrium; For a dynamic equilibrium to be set up, the rates of the forward reaction and the back reaction have to become equal. This doesn't happen instantly. For a very slow reaction, it could take years! A catalyst speeds up the rate at which a reaction reaches dynamic equilibrium. -*a change in temperature will alter equilibrium*. For exothermic reactions increasing temperature will decrease Keq and for endothermic reactions increasing temperature will increase Keq; -lowering the energy of activation will impact rate, but does nothing to equilibrium; -stabilizing the transition state is essentially the same as lowering the energy of activation and will not impact equilibrium; -adding reactants or products will do NOTHING to equilibrium. What you have done is suddenly move the reaction away from its equilibrium—but equilibrium didn't move or change. Equilibrium is still the same specified ratio of products/reactants -a state to which the reaction will now attempt to return.

Cations vs. Anions

-Any atom or molecule with fewer electrons than protons is a cation. ( cations are pawsitive) -Any atom or molecule with more electrons than protons is an anion.

Avogadro's Number

6.022 x 10^23 number of atoms/ molecules ions/ in one mole

Ionic Character

All bonds that are *not* between two atoms of the same element have some ionic character. -It is basically a measure of the polarity of the bond. Ionic species such as NaCl have close to 100% ionic character. -Covalent bonds between two non-metals of nearly identical electronegativity have close to zero ionic character.

Decomposition Reaction

A decomposition reaction is one where a molecule breaks apart into simpler ones And an example of it occurs when hydrogen peroxide breaks apart to form oxygen gas and water: 2 H₂O₂ → 2 H₂O + O₂

Actual Yield

Actual yield is just what it sounds like, the amount of product in grams you obtain at the end of the actual experiment in the lab.

Cyanide (memorize formula and charge)

CN-

Carbonate (memorize formula and charge)

CO3 2-

Use a reaction coordinate diagram to explain why the heat of combustion is greatest for the most unstable molecules?

Carbon dioxide and water, compared to most other reactants or products, are very stable. Therefore, whenever you graph a combustion reaction you will expect the products to be very low on the y-axis (Energy). The heat of combustion, ∆Hcombustion, for the reaction will be equal to the difference in height between the products and reactants. So, the more unstable the starting products are, the higher they will be on the graph, and therefore the greater will be the difference in height between products and reactants.

Gamma Emission

Gamma rays are usually emitted as a byproduct of the types of decay outlined above. -very high energy -Gamma decay *does not change the number of nucleon*

Ionic Bonds

Ionic bonds are usually formed a between a *metal and a non-metal and are due to an electrostatic attraction*. ***They can also be between two charged non-metals Ex:NH4Cl -almost always exist as solids at room temp They can be conceptualized in two ways. 1) You can visualize the two species as previously formed ions. For example, Na+ and Cl-. It is fairly obvious that these two species will be strongly attracted to one another by an electrostatic force. 2) *you can also visualize it as if the two atoms came together in their ground states (not as ions) and the more electronegative atom (Cl- in this case) pulled one electron completely away from sodium. This would result in essentially the same result, a sodium cation and a chloride anion.*

Whichtwoelementsintheperiodictable,ifunitedinabond,wouldcreateabondwiththe maximum possible ionic character?

Ionic character is due to a difference in electronegativity between the two atoms in a bond. So, a C-C bond, for example, would have zero ionic character. Theoretically, the greatest possible ionic character would exist in francium fluoride. However, francium is extremely unstable with a half- life of around 20 minutes. It also happens to be among the rarest of all elements, so it is unlikely that francium-fluoride has ever been formed.

The Law of Mass Action:

Keq = [products]^x/ [reactants]^y -Keq is written with every term raised to an exponent equal to its coefficient in the balanced equation -*Pure liquids (l) and pure solids (s) are never included!* -solids are not included because they cannot react in the crystal lattice. Look for ionic bond they will exist as solids!!! -liquids are not included because the molecules are not dispersed they are just interacting with themselves (think oil and water) -This situation we call "equilibrium" is described mathematically by the ratio of products over reactants present at that exact point. We calculate that ratio using the law of mass action and the resulting number we call Keq. We like students to think of Keq as exactly that—a mathematical number used to define/describe/label equilibrium. This works nicely because this state of maximum "happiness" for the reaction in terms of energy and entropy is dependent on a certain ratio of reactants to products. If the amount of either of these changes, the number we calculate for Keq will also change and then we will know that we are no longer at that ideal set of conditions (In fact, the minute that number changes we don't even call it Keq anymore, we call it Q instead). *equilibrium and reaction rate describe totally different things.* -A high number for Keq simply tells us that at equilibrium there will be a lot more products than there are reactants. This tells us the reaction is spontaneous and will strongly favor the products side of the reaction, but tells us nothing about how fast it will get there.

Iron, like other transition metals, shows limited reactivity. Most reactions must be catalyzed by a strong acid. The Keq for such an acid catalyst would be: A. close to 1. B. less than 1. C. much greater than 1. D. much less than 1

Keq is the ratio of products over reactants raised to their coefficients in the balanced equation. Because strong acids, by definition, dissociate 100%, the Ka will be the ratio of nearly 100 percent product over almost no reactant—a very large number. This makes C the only logical answer.

Ammonium (memorize formula and charge)

NH4+

Nitrite (memorize formula and charge)

NO2-

Nitrate (memorize formula and charge)

NO3-

Naming General Ionic Compounds

Name the cation first, then the anion (i.e., calcium sulfate is CaSO4, not SO4Ca, and is not called "sulfate calcium")

Binary Compounds

Name the element furthest down and to the left on the periodic table first; use poly prefixes as necessary (e.g., Nitrogen Trioxide, Carbon Monoxide, Sulfur Dioxide, etc.). -Some have common names such as ammonia and water. *SEE EMP LINKS FOR PRACTICE*

Naming Monoatomic Atoms (anions)

Named by replacing the last syllable with "-ide." (e.g., sulfide ion, hydride ion, chloride ion, etc.)

Nitrate vs Nitrite

Nitrate (+) Nitrite (-)

Hydroxide (memorize formula and charge)

OH-

Phosphate (memorize formula and charge)

PO4 3-

Calculating Percent Mass of an Element

Percent Mass = (mass of one element/total mass of the compound)(100%) A similar term "wt-wt percentage" has essentially the same formula (massx/total mass x 100), but is used for solutions. In this case, the mass referred to is usually the mass of the solute and the total mass is the mass of the entire solution.

Mole to Mole Conversion

Density = g/mL Molarity = moles/ Liter

Spectator ions

Don't participate in the reaction

Flash Point

Flash point does increase going down a family of metals, but doesn't explain reactivity with water because flash point is the temperature at which a metal basically decomposes or explodes.

Collisions Cause Reactions!

For a reaction to occur: 1) The reactants must collide with enough energy to overcome the energy of activation 2) The reactants must be in the correct spatial orientation

When you disrupt the equilibrium, creating a "shift" according to Le Chatelier's principle, what happens to Keq? Does it change?

Le Chatelier's principle states that if the reaction is already at equilibrium adding either products or reactants will cause the reaction to suddenly be AWAY from its equilibrium and the reaction will then proceed in whatever direction necessary to relieve that stress and RETURN to equilibrium, but equilibrium—as defined by Keq—did not move or change. -In other words, the value of the equilibrium constant for that reaction does not change just because we added a stress to the system. -Contrast this to changes in temperature which actually DO change the equilibrium state and therefore the Keq. -We dislike the fact that many sources use terms like "shift the equilibrium" when talking about Le Chatelier's Principle because it gives students the wrong idea that dumping in a few extra reactants changed the equilibrium state for that reaction. - No. It absolutely did not. Students need to think of equilibrium as a law of nature—for any set of reactants and products at a given temperature the ideal, lowest energy, highest entropy state is fixed—it is predetermined by the permanent characteristics of the reactants and products themselves. *Temperature is the ONLY thing that actually changes equilibrium, Keq*

The solubility of metal hydroxides in water is: A. increased by the addition of a strong acid. B. increased by the addition of hydroxide ions. C. greater at high pH values. D. unaffected by pH.

LeChatelier's principle question. It does, however require a bit of acid/base background. First, draw out the dissolution equation. Any metal hydroxide will break apart into the metal ion and one or more hydroxides. Answer A, addition of strong acid would result in the OH- being protonated. This would remove OH- and thus shift the equation to the right, increasing solubility.

Metals form_______ ,but non-metals form_______ .

Metals for cations Ex Mg+ Non-metals for anions Ex: O-

Manganite (memorize formula and charge)

MnO4 2-

Permanganate (memorize formula and charge)

MnO4-

Cations are smaller than their neutral counterpart and anions are larger than their neutral counterpart. Q4. Why? Explain the difference in size between anions, cations, and neutral atoms.

Most cations that form do so by losing electrons to match the electron configuration of the nearest noble gas. -This means they will have lost an entire shell, and therefore considerable volume. -Anions are larger because they have gained electrons which will take up additional space in their electron cloud, particularly because electrons repel one another.

Bonding and Anti-Bonding Orbitals:

Most of this is beyond the MCAT. Just remember the following: 1) *Anti-bonding* orbitals are *higher in energy* than bonding orbitals. 2)* Bonding orbitals contain electrons that are "in phase" and are said to be "attractive"*; -*anti-bonding orbitals contain "out of phase" electrons that are said to be "repulsive."* 3) Know what drawings of bonding and anti-bonding orbitals look like.

Double Displacement ("metathesis reaction")

Also called a double "replacement" reaction, this type of reaction occurs when the *cations of two chemical compounds switch places*. The general form for this reaction is: AB + CD → CB + AD Another example: HCl + AgNO₂ → AgCl + HNO₂

Isotopes

An isotope is one of multiple versions of the same atom that have *differing numbers of neutrons* -All isotopes must have the* same Z number because it is the number of protons that defines the atom as a specific element* (carbon, hydrogen, etc.). -If you know the Z number you know the element. All isotopes do not have an odd mass number (carbon-14), although many do (iron-57). (protium is the common stable isotope)

Atomic Weight/Molar Mass

Atomic weight is usually defined as the mass of one mole of any atom (in grams) -the "g/mol" measurement given in the periodic table for individual element

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.

Alpha Decay

The loss of one He nucleus, which has a mass number of 4 and atomic number of 2. -Note that an alpha particle is only the He NUCLEUS—it has no electrons! -two neutrons and two protons -He has 2+charge when emitted bc no electrons

Electronegativity

a measure of the ability of an atom in a molecule to draw *bonding electrons* to itself.

Valence Electrons

an electron of an atom, located in the outermost shell (valence shell) of the atom, that can be transferred to or shared with another atom.

Molecular Weight

molecular weight, the sum of those measurements (of atomic weight) for all of the atoms in a molecule. -the "g/mol" measurements given in the periodic table for individual element

Larger atoms

better at stabilizing charges, don't form pi bonds and have d orbitals where they can "house" extra electrons. Larger atoms form weaker pi bonds because of a decrease in the overlap of the p orbitals.

Sulfate vs sulfite

both are charged 2-

Bicarbonate (memorize formula and charge)

HCO3-

First Quantum Number:

a.k.a. "n" or "the principle quantum number" -Gives the shell (e.g., valence electrons are in the outermost "shell") and represents the relative energy of electrons in that shell. - "approximately" equal to the energy of electrons in that shell (Not really bc 3d has more energy than 4s)

Positron Emission

A proton emits a positron (e+) and is changed into a neutron (protons = neutron+ positron)

Electron Capture:

A proton is changed into a neutron via capture of an electron. -neutron= proton + electron

Reversible reactions

A reversible reaction is one which can be made to go in either direction depending on the conditions.

Zeffective (effective nuclear charge)

As atoms increase in size, they are surrounded by more and more electrons. - The "effective nuclear charge," felt by the valence electrons of such atoms is less than expected -This is because the electrons in between the valence shell and the nucleus "shield" the valence electrons, preventing them from feeling the full charge of the nucleus. Hydrogen's electron feels its full nuclear charge because there is zero shielding.

Why can temperature change key?

At high temperatures the reaction can proceed in either direction (enough energy to reach both activation energies) so equilibrium arrows may change

Periodic Table trends are largely dependent on

Atomic radius!!!!

Combination/Synthesis Reaction

A synthesis reaction is a reaction in which simple compounds are combined to make a more complex one.

Bond Length (Covalent Bonds only)

distance between the nuclei of the atoms forming the bond

Sulfate (memorize formula and charge)

SO4 2-

Second Order Reactant

double reactant = quadruple rate 1/[A] vs. time is linear with slope = k For a 2nd order reaction, rate = k[A]2 (k = slope of line)

First Order Reactant

double reactant= double rate ln[A] vs. time is linear with slope =-k For a 1st order reaction, rate = k[A] (k = - slope of line)

What is the expected condosity of a 3.0M LiCl solution?

Sodium is more metallic than lithium, so we would expect an NaCl solution to conduct electricity better than an equimolar LiCl solution. This means the NaCl solution would need to be less concentrated in order to conduct equally as well. This predicts a condosity of something less than 3.0 for a 3.0M LiCl.

Le Chatelier's Principle:

Systems already at equilibrium, that experience change, will shift to the left or to the right to reduce the effects of that change and re-establish equilibrium.

Coordinate Covalent Bonds

formed when one atom donates both of the electrons to form a single covalent bond. These electrons originate from the donor atom as an unshared pair. -a lone pair on nitrogen contributes 2 electrons to form the ammonium ion. All of the bonds in these ions are indistinguishable once formed, however.

Combustion Reaction

Combustion reactions take place when a compound containing carbon and hydrogen reacts with oxygen to make water vapor, carbon dioxide, and heat. This sounds annoying, I know, but it's really not. Consider the general form of a combustion reaction: CH + O₂ → CO₂ + H₂O Basically, if anything containing C and H reacts with oxygen gas, you end up with carbon dioxide and water vapor. And lots of heat

Percent Yield

The percent yield is just the ratio of the actual yield over the theoretical yield multiplied by 100.

Why do bonds form?Is energy required or released when a bond is formed?

*Atoms are without feelings and don't "want" to form bonds* -*They only do so in situations where the resulting bond is a lower energy state than was the unbonded form (or than the previous bonds they were engaged in with other atoms)*. -As a result, *forming bonds always releases energy*. This is a major point of confusion for students. ATP is often the molecule that exacerbates this confusion. The transition from ATP to ADP does release energy, but only because the forming of the new bonds in ADP releases more energy than was required to break the bonds in ATP—NOT because breaking the bonds in ATP released energy. -*forming a lower energy, more stable, molecule requires release of energy*

Good vs. Poor Electrolytes

*Covalent compounds that dissociate 100% in water, such as strong acids and strong bases, make good electrolytes.* -Other covalent compounds are usually poor electrolytes. -*Ionic compounds that are soluble in water always make good electrolytes.* -strong acids HCl, HBr, HI, HNO3, HClO3, HClO4, and H2SO4 -strong bases NaOH, KOH, LiOH, Ba(OH)2, and Ca(OH)2 -salts NaCl, KBr, MgCl2, and many, many more-

Rate Order Graphs

These graphs will only be linear when the reaction has only a single reactant, OR when it is part of a multiple-reactant reaction where the rate is independent of ALL the other reactants (e.g., the other reactant is zero order, or is in excess). reactants can be nth order -when measuring one reactant must be in excess so that you are measuring with respect to one variable -0 order reactants not included in the rate law -if there is a linear line there is definitely only one reactant contributing -if line is not linear could be for 2 reasons 1) wrong graph 2) two reactants contributing to the rate

How many hydrogen atoms are present in 2.0 g of water?

Convert grams of water into moles of water by dividing by the molecular weight of water (18 g/mol). Next multiply by the factor 2 moles H atoms/1 mole of H2O. This cancels moles of water and leaves you with moles of H atoms. However, the question does NOT ask for moles of H atoms, it asks for how many; thus, you must multiply by Avogadros number, 6 x 1023. This gives 1.33 x 10^23

Bond Dissociation Energy (Covalent Bonds Only)

it is the same as bond energy, the amount of energy required to break or "dissociate" the bond.

A chemist prepares a solution by adding 200 mL of 0.80 M Fe2(SO4)3 to 2.0 L of water. How many moles of sulfate ions are present?

This is a mole-to-mole conversion problem. They should be pretty straightforward, but they are often missed. Make sure you UNDERSTAND how to do them, then focus on not making dumb math mistakes. You will definitely see a few on your MCAT. In this case, multiply the M (moles/L) by the volume in liters (0.2L) to get 0.16 moles of Fe2(SO4)3. If you forget to change milliliters to Liters, you'll get the wrong answer. Next, you must notice that for every one mole of iron sulfate there are 3 moles of sulfate ions. Multiplying the previous answer by 3 gives Answer B, 0.48, or 4.8 x 10-1.

dynamic equilibria Thinking about reaction rates

This is the equation for a general reaction which has reached dynamic equilibrium: How did it get to that state? Let's assume that we started with A and B. At the beginning of the reaction, the concentrations of A and B were at their maximum. That means that the rate of the reaction was at its fastest. As A and B react, their concentrations fall. That means that they are less likely to collide and react, and so the rate of the forward reaction falls as time goes on. (see picture) At this point where the rates become equal, there won't be any further change in the amounts of A, B, C and D in the mixture. As fast as something is being removed, it is being replaced again by the reverse reaction. We have reached a position of dynamic equilibrium.

Third Quantum Number:

"ml" or "the magnetic quantum number" o Gives the orbital orientation; has a value of -l to l (from the azimuthal quantum number) Designates the orientation of the subshell where an electron is most likely to be found (i.e., which "dumbbell" of a p subshell)

Empirical vs. Molecular Formulas

*Empirical formulas represent the lowest possible number of moles of each element that can be present in a compound while still maintaining the same mole-to-mole ratio between the elements.* -*A molecular compound is the actual number of moles of each element found in a specific compound*. For example, CH2O is the empirical formula for glucose, and C6H12O6 is the molecular formula for glucose. However, CH2O is also the empirical formula for all other carbohydrates. -The subscripts for a molecular formula and its empirical formula will always differ by a factor of some whole integer. The two formulas can be the same. For example, the empirical formula for water is also the molecular formula. *Molecular formula consists off all molecules*

Name Acids

*Follow the "ate-ic - ite-ous" convention.* - If the ion name ends in "-ate," replace that ending with "-ic" as in: Nitrate -> Nitric Acid. -If the ion name ends in "-ite," replace that ending with "-ous" as in: Nitrite -> Nitrous Acid. -If the parent is a single ion rather than a polyatomic ion, replace the "ide" ending with "-ic" and add "Hydro-" as a prefix, as in: Iodide Hydroiodic Acid.

Rates of Multi-Step Reactions

*If there is a slow step, the slow step always determines the rate* -If the slow step is first, the rate law can be written as if it were the only step. -If the slow step is second (based on a few assumptions that are beyond the MCAT) the rate law is the rate law of the slow step—which will include an intermediate as one of the reactants.*

How will increasing each of the following affect reaction rate: [reactants], [products], [catalyst], energy of activation (Ea), energy of the transition state, energy of the reactants, and temperature?

-Increasing the concentration of the reactants will increase the rate of the reaction as long as the reactant in question is in the rate law; -increasing the concentration of products has no effect on reaction rate [Note: This might be a good place to emphasize that kinetics is usually studied only for the very, very early stages of a reaction - the initial rate method - when all reactants and catalysts are available in excess]; -increasing the concentration of a catalyst will increase rate; increasing the energy of activation or the energy of the transition state (which would increase the energy of activation) decreases rate at constant temperature; -increasing the energy of the reactants would make them closer to the energy of activation and would therefore increase rate; -increasing the temperature will increase the average KE of the reactants and therefore increase rate; [Note: Increasing the concentration of a catalyst can produce diminishing returns. Having more catalyst, for example, increases the likelihood that the reactants and the catalyst will interact. However, if you had 1,000 times more catalyst molecules than you have reactant molecules, adding more catalyst at that point would have little effect on the rate - a graph of rate vs. concentration of a catalyst approaches a horizontal asymptote.]

Rate Laws

-Know how to write a rate law, how to determine one from a table of experimental values, and how to predict experimental results based on a given rate law. Rate laws assume the following: 1) Reactions only proceed forward (we ignore the reverse reaction) 2) We only consider the first few seconds of the reaction, when there is a high concentration of each reactant and any catalysts (e.g., enzymes). The exponents equal the "order" of each reactant. Only if you are specifically told that the reaction is "elementary" do the coefficients equal the exponents in the rate law

Predict the effects of doing each of the following to a reaction at equilibrium: 1) adding/removing reactants, 2) adding/removing products, 3) increasing/decreasing pressure, and 4) increasing/decreasing temperature.

1) Adding reactants will shift the reaction to the right; Removing reactants will shift the reaction to the left; 2) Adding products will shift the reaction to the left; Removing products will shift the reaction to the right; 3) Increasing pressure will shift the reaction toward the side with fewer moles of gas; Decreasing pressure will shift the reaction toward the side with more moles of gas; he action that will increase the pressure in a reaction vessel is any disturbance that will push the equilibrium toward the side of the reaction containing more moles of gas. 4) Increasing temperature will actually CHANGE the Keq and will shift the reaction. IF the reaction is exothermic increasing temperature will shift the reaction to the left and the Keq will decrease. If the reaction is endothermic increasing temperature will shift the reaction to the right and Keq will increase. The effect of decreasing temperature will have the exact opposite impact described for each type of reaction.

Step-by-Step Instructions for Balancing a Reaction:

1) Balance the number of carbons 2) Balance the number of hydrogens 3) Balance the number of oxygens 4) Balance the number of any remaining elements 5) If necessary, use fractions. For example, if you have seven oxygens on one side of the reaction and one O2 on the other side, put 7/2 in front of the O2. 6) Multiply all of the species on both sides of the reaction by the denominator of any fractions. 7) Double check your work by counting the number of atoms of each element found on each side of the reaction. *One of the most common errors is failure to multiply by a coefficient*. For example, you might accidentally count 2CO2 as 2 oxygens when there are actually 4 oxygens present. *You must double-check every reaction you see on the MCAT to ensure that it is balanced. Yes, they will give you unbalanced reactions without telling you*

Deriving a Formula from Percent Mass

1) Change the percent mass for each element into grams (i.e., 15% = 15g). 2) Convert the grams of each element into moles by dividing by molar mass. 3) Look at the element with the lowest number of moles. Calculate approximately how many times it will divide into each of the other molar amounts for each of the other elements—this number will be the subscript for each element in the empirical formula. If the subscripts are not at their lowest common denominator, reduce to get the empirical formula. -The moles you come up with are NOT the subscripts in the empirical formula, or even in a molecular formula. These numbers only tell us the relative ratio between the different compounds. *An empirical formula is all you can get from percent mass alone.* To get the molecular formula, you must be given the MW of the unknown compound. If you have the molecular weight of the actual compound, simply divide that MW by the MW of the empirical formula. You should get a whole number. Multiply each subscript by that number to get the molecular formula.

To calculate the "order" of each reactant using experimental data:

1) Find two trials where the [reactant] in question changed, but all other parameters did NOT (i.e., the concentrations of the other reactants, temperature, pressure, etc., all remained constant). only that reactant's concentration should change 2) Note the factor by which the reactant concentration changed. 3) Note the factor by which the rate changed across those same two trials. 4) Solve for Y in the following equation: X^Y = Z ; where X = the factor by which the [reactant] changed, Z = the factor by which the rate changed, and Y = the order of the reactant. Recall that any number raised to the zero power is equal to one. -The "overall order" of a reaction = the sum of the exponents in the rate law -Be careful whenever you see temperature. It is meaningless to compare two trials with different temperatures, so find two where only one concentration changed and both the other reactant's concentration AND the temperature remained constant. http://bouman.chem.georgetown.edu/S02/lect2/lect2.htm

Order progressing through the periodic table to fill orbitals

1) between the s-block and d-block, where they need to know that the first d-block row is a 3d even though the orbital filled just prior to it was a 4s, *3d has more energy than 4s* 2)2) between the s-block, f-block, and d-block in rows 6 and 7; where they need to know that the lanthanide and actinide series are filled before proceeding with rows 6 and 7 respectively. lanthanide = 4f actinide = 5f

Catalysts

A catalyst is any substance that increases reaction rate without itself being consumed in the process. -Catalysts change the rate of the reaction by offering an alternate route for the reaction with a lower energy transition state and therefore a lower energy of activation. [It may not be technically true to say that catalysts "lower the activation energy" simply because the "normal" uncatalyzed reaction will still be going on for some other molecules not interacting with the catalyst. -assume that if a catalyst is present all of the molecules will react via the catalyst and therefore it would be safe to say that the catalyst lowered the energy of activation. -They do NOT change the equilibrium, Keq, enthalpy change, entropy change, Gibbs free energy, or any other thermodynamic properties. -The MCAT uses this question type heavily and students are often tricked into accepting a false concept such as: "adding a catalyst will increase percent yield

closed system

A closed system is one in which no substances are either added to the system or lost from it. Energy can, however, be transferred in or out at will.

Beta Decay

A neutron emits an electron to become a proton with the ejection of an electron -beta particle is emitted electron -neutron= proton + electron

Single Displacement

Also known as a "single replacement reaction", this type of reaction occurs when a pure element switches places with an element in a chemical compound. Essentially, two atoms switch places, where one of the atoms isn't stuck to anything else. The general form of this reaction is: A + BC → B + AC In this case, the elements A and B switched places. This type of a reaction is also a very common type of redox reaction Many metals will boil when you place them into a strong acid. For example, if you put magnesium into hydrochloric acid, you'll get the following single-displacement reaction: Mg + 2 HCl → H₂ + MgCl₂ Because hydrogen is a gas, bubbles can be seen during this reaction.

Redox Reactions

Always occurs in pair Ca(s) + 2H2O(l) -> Ca2+ + H2(g) + 2OH- This is not possible bc not electron gained in run Ca(s) + H2O(l) -> H2O(g) + Ca2+

"Identify the gas" Problem

Always try to narrow your choices first by ruling out gases that would be impossible (i.e., they contain elements that aren't even in the reaction) or seem very illogical. Next, look at the actual molecules involved and figure out how they would have to break up and re-bond in order for each remaining gas. Often you will see illogical things happening here too. Remember that reactions don't occur spontaneously unless something favorable is happening. Also remember that water is VERY often a product or reactant in these reactions. It may help to ask yourself, "If I formed water or used water, what would be left over?" In this case, you are helped by the electron configuration. You should know that since a lot of energy is being released, Sr is probably going to a much lower energy state, such as its noble gas configuration

Energy Levels & Photon-Light Emission

Because energy levels are quantized, you cannot cause an electron to move up one energy level unless you add an amount of energy equal to the difference in energy between the current energy level and the higher energy level. -If an electron is struck by a photon with an energy that is lower than the difference in energy between two energy levels in that atom the photon will pass through the atom without being absorbed. -If an electron drops to a lower energy level, energy is released as a photon (i.e., as electromagnetic radiation). -The energy released will be exactly equal to the difference between the two energy levels.

A certain metal is known to have a work function of 500J. If a photon of 500J strikes the surface of the metal, what will be the result?

Because the energy of the photon exactly equals the work function nothing will happen. Theoretically, it is as if the electron is now "freed" from its attraction to the nucleus but cannot move because it lacks any excess energy to transfer into KE.

The Work Function

Bombarding certain metals with energy can cause the ejection of an electron from their outermost shell (i.e., valence electron). -The amount of energy required to do this is called the "work function," and is usually given the variable φ. This may sound similar to "Ionization Energy." - However, they are NOT the same. Ionization energies are measured for lone atoms in a gaseous state. -*The work function refers specifically to valence electrons being ejected from the surface of a solid metal.* -* If the energy added is less than the work function, the electron won't be ejected. If it is greater than the work function, the excess energy will be transferred into the kinetic energy of the ejected electron.* KE=E-φ ; where -E is the amount of energy added and -KE is the kinetic energy of the ejected electron. -Because energy is usually added via bombardment with photons, E can be replaced with hf, the formula for the energy of a photon. E = hf ; -where E = the energy of a photon, -h = Planck's Constant (which is always given) and -f = frequency.

Hypochlorite (memorize formula and charge)

ClO-

Chlorite (memorize formula and charge)

ClO2-

Chlorate (memorize formula and charge)

ClO3-

Perchlorate (memorize formula and charge)

ClO4-

Periodic Table: Group/family

Columns *families have similar properties* -Elements in the same family (column) tend to have similar properties, both chemical and physical (e.g., SiH4 will behave similar to CH4). -Whenever you are asked for "another element" that will react "similarly" to a given element, the right answer will almost always be an element in the same family or group. Although elements in the same period and only differing by one proton may be more similar in size, reactivity and physical characteristics are most similar among elements in the same family

Heat of Combustion (Covalent Bonds Only)

Combustion reactions always involve molecular oxygen O2. Anytime anything burns (in the usual sense), it is a combustion reaction. Combustion reactions are almost always exothermic (i.e., they give off heat). -the amount of energy released when a molecule is combusted with oxygen. -All covalent bonds are broken and reformed in a radical reaction. -*The higher the energy of the molecule (i.e., less stable) the higher the heat of combustion.*

Covalent Bonds

Covalent bonds are usually formed between *two non-metals and involve sharing of electrons within the bond*. -This sharing need not be equal, and is in fact usually not due to differences in electronegativity. Ionic bonds are usually formed a between a metal and a non-metal and are due to an electrostatic attraction. They can be conceptualized in two ways. First, you can visualize the two species as previously formed ions. For example, Na+ and Cl-. It is fairly obvious that these two species will be strongly attracted to one another by an electrostatic force. Alternatively, you can also visualize it as if the two atoms came together in their ground states (not as ions) and the more electronegative atom (Cl- in this case) pulled one electron completely away from sodium. This would result in essentially the same result, a sodium cation and a chloride anion. -Covalent molecules are not good conductors unless they happen to be good electrolytes. Even then, it is the solution of the ions in water that is a good conductor, not the pure compound itself (HCl is an example)

Energy Levels of the Bohr Model of an Atom

Electrons can and do jump from one level to another if they receive the exact quantum of necessary energy and will release a photon equal in energy to the difference between two energy levels when they "relax" back to a lower energy level. -electrons fill up orbitals from lowest energy to highest energy 1s2, 2s2, 2p6, 3s2,3p6...... see chart for shapes of where electrons would appear

Equillibrium- Relate to Gibbs Free Energy

Equilibrium is the state reached in the progress of a reversible reaction wherein there ceases to be any additional NET progress in either the forward or reverse direction. -The reaction is still proceeding to a very small degree in both directions, but these movements cancel one another out. -Under those exact conditions the entropy for that reaction is at its maximum possible value. Those conditions are also the lowest possible energy state for that reaction. -Gibbs Free Energy will be exactly zero at equilibrium. This makes complete sense because the reaction would not proceed spontaneously in either direction because it is already at its most favorable state. -This situation we call "equilibrium" is described mathematically by the ratio of products over reactants present at that exact point

Quantum Mechanics

Every electron in an atom has a unique "address" or "location." -shell -subshell -orbital -Spin (+1/2 or -1/2)

Insulation

Recall that conduction of electricity involves electrons in the outermost shell being bumped from one atom to another. -Thus, a high energy of ionization would be a barrier to conduction.

Increasing Yield

Remember that yield is a function of reactants and equilibrium, NOT rate. *Thus, adding a catalyst may increase rate, but will NOT increase yield*. For the MCAT, focus on these two ways to increase yield: 1) Start with more reactants -will increase overall quantity of yield, but *NOT PERCENT YIELD*. Furthermore, it will only work if you *add more of the limiting reagent*. Adding more of any non-limiting reagent (i.e., a reagent that is in excess) will have no effect. 2) Shift the equilibrium to the right using one of the actions described by Le Chatelier's Principle -The most common method of shifting the equilibrium in this way is to remove products as they are formed. By doing so, you force the reaction into a constant state of "catch up." The reaction continually produces more product in an attempt to reach equilibrium.

Energy levels

Represent the energies of the electrons in an atom. -They are quantized! In other words, they look like stair steps, and do NOT look like a ramp. -Electrons can be in energy level 1 or energy level 2, but never anywhere in between.

Periodic Table: Period

Rows

Rutherford Gold Foil Experiment

Rutherford's Nuclear Atom Experiment In 1910, Rutherford and his coworkers were studying the angles at which alpha particles were scattered as they passed through a thin gold foil. Most particles passed through undeflected, though a few were found to be scattered at large, some even in the direction they had come. This meant they had collided with an object much more massive than the particle itself, but so small that only a few aplha particles encountered them. Showing that the atom was composed of a small dense massive center surrounded by low mass electrons. https://www.youtube.com/watch?v=5pZj0u_XMbc

Why Size Matters

Smaller atom's nuclei are closer to their valence electrons, so according to Coulomb's Law, F = kqq/r2, those electrons are held more tightly to the positively charged nucleus. -This greater force will also cause the atom to be more electronegative, have a higher ionization energy, greater electron affinity and less metallic character than a larger atom

Electrolytes

Substances that give ions when dissolved in water are called electrolytes. They can be divided into acids, bases, and salts, because they all give ions when dissolved in water. -These solutions conduct electricity due to the mobility of the positive and negative ions, which are called cations and anions respectively. Strong electrolytes completely ionize when dissolved, and no neutral molecules are formed in solution. -Some other ionic solids are NaCl, CaCl2, NH4Cl, KBr, CuSO4, NaCH3COO (sodium acetate), CaCO3, NaHCO3 (baking soda).

Whenever you see a question about why something is a gas, liquid, solid, etc., or why it takes a lot of energy to go from one phase to another...

THINK INTERMOLECULAR FORCES

Metals

THINK OF METALS AS: -larger atoms with loosely held electrons. -Metals "like" to lose electrons and form positive ions. -They are lustrous, ductile, malleable and excellent conductors of both heat and electricity. They are involved in ionic bonds with nonmetals. -react with water to form metal hydroxides + H2 -When a metal reacts violently with water it is because the metal is ionizing, or releasing electrons. -Remember, metals have a sea of loosely held electrons, and it would make sense that they would give electrons up more easily.

Non-metals

THINK OF NON-METALS AS: -smaller atoms with tightly held electrons. -Non- metals "like" to gain electrons and form negative ions. -They have lower melting points than metals, and form covalent bonds with non-metals. -form ionic bonds with metals -Most of the O-Chem stuff involves non-metals.

Rate Laws for Catalyzed Reactions

Technically,the rate law is the sum of the rate law for the uncatalyzed reaction and the rate law for the catalyzed reaction. This fact, however, can usually be ignored, and *you can assume that the rate law for the reaction is exactly equal to the rate law for the catalyzed reaction alone* -Under such an assumption, *write the rate law in the same way as normal, with the concentration of the catalyst added in as a reactant. The rate constant, k, is sometimes replaced with kcat* -The uncatalyzed reaction usually proceeds at a rate that is much slower than the catalyzed reaction. Therefore, the products from the reaction will be almost exclusively result from the catalyzed pathway. We can ignore the parallel uncatalyzed reaction because even though we know it is occurring simultaneously, its contribution to the progress of the reaction is negligible..

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*. For example, for a 2.0 M KCl solution, we would expect the condosity to be something more than 2.0. Why would we expect it to be above 2.0? Because potassium is more metallic than sodium. Thus, we know that it will be a better conductor. This means the NaCl solution will have to be slightly more concentrated in order to conduct electricity as well as the KCl solution. -the more metallic an ion is, the better electrolyte it will be in solution, which will make it a better conductor. *METALLIC CHARACTER INCREASES WITH ATOMIC RADIUS* *Remember this as a periodic trend, condosity increases as you move down and to the left on the periodic table because you will need ore NaCl* -same trend as atomic radius

The Reaction Quotient

The Equilibrium Constant can only be calculated at equilibrium. If you make the exact same calculation using concentration values taken at any point other than equilibrium the result is called the Reaction Quotient, Q. -If Q > K, the reaction will proceed to the left or reactants. -If Q < K, the reaction will proceed to the right or products. -Recall that both K and Q are ratios of products over reactants. K is the exact ratio at equilibrium and Q is the ratio taken at any other point of the reaction. Because the products go in the numerator, if Q is greater than K, this means we must have more products than we do at equilibrium. If Q is less than K, this must mean we have more reactants than we do at equilibrium (because the reactants go in the denominator). The question says Q > K, so to get rid of excess product and go to equilibrium, the reaction will need to proceed to the left

Heisenberg Uncertainty

The Heisenberg Uncertainty Principles states that the more we know about an electron's position, x, the less we know about its momentum, p. The position and momentum of a particle cannot be simultaneously measured with arbitrarily high precision

The Strong Nuclear Force

The Strong Nuclear Force (also referred to as the strong force) is one of the four basic forces in nature (the others being gravity, the electromagnetic force, and the weak nuclear force). -As its name implies, it is the strongest of the four. However, it also has the shortest range, meaning that particles must be extremely close before its effects are felt. -Its main job is to hold together the subatomic particles of the nucleus (protons, which carry a positive charge, and neutrons, which carry no charge. These particles are collectively called nucleons). -As most people learn in their science education, like charges repel (+ +, or - -), and unlike charges attract (+ -). -The protons must feel a repulsive force from the other neighboring protons. This is where the strong nuclear force comes in. -The strong nuclear force is created between nucleons by the exchange of particles called mesons. -This exchange can be likened to constantly hitting a ping-pong ball or a tennis ball back and forth between two people. -As long as this meson exchange can happen, the strong force is able to hold the participating nucleons together. -The nucleons must be extremely close together in order for this exchange to happen. The distance required is about the diameter of a proton or a neutron. -If they can't get that close, the strong force is too weak to make them stick together, and other competing forces (usually the electromagnetic force) can influence the particles to move apart. -This is represented in the following graphic. The dotted line surrounding the nucleon being approached represents any electrostatic repulsion that might be present due to the charges of the nucleons/particles that are involved. A particle must be able to cross this barrier in order for the strong force to "glue" the particles together. In the case of approaching protons/nuclei, the closer they get, the more they feel the repulsion from the other proton/nucleus (the electromagnetic force). -As a result, in order to get two protons/nuclei close enough to begin exchanging mesons, they must be moving extremely fast (which means the temperature must be really high), and/or they must be under immense pressure so that they are forced to get close enough to allow the exchange of meson to create the strong force. . -One thing that helps reduce the repulsion between protons within a nucleus is the presence of any neutrons. Since they have no charge they don't add to the repulsion already present, and they help separate the protons from each other so they don't feel as strong a repulsive force from any other nearby protons. -Also, the neutrons are a source of more strong force for the nucleus since they participate in the meson exchange. These factors, coupled with the tight packing of protons in the nucleus so that they can exchange mesons creates enough strong force to overcome their mutual repulsion and force the nucleons to stay bound together. -The preceding explanation shows the reason why it is easier to bombard a nucleus with neutrons than with protons. Since the neutrons have no charge, as they approach a positively charged nucleus they will not feel any repulsion. They therefore can easily "break" the electrostatic repulsion barrier to being exchanging mesons with the nucleus, thus becoming incorporated into it. -

Adaptations Made to the Bohr model

The dual- nature of electrons—namely that they show both wave-like and particle-like nature similar to light. -Second, electrons do NOT orbit the nucleus in circular planetary-like patterns resembling the rings of a target. -Remember that the electrons are contained in s, p, d and f orbitals with unique shapes. -Orbitals are not actual boundaries but mathematical wave functions that predict the probability of where an electron could be at any given instant. -We would expect the electron to be somewhere within that orbital (as defined by that shape) even though the orbital itself has no physical boundaries. -Instead of thinking of electrons as being added to an atom in the oversimplified 2 + 8 + 8 . . . pattern, explain orbital filling corresponds to modern electron configuration diagrams—specifically to the number of electrons that can be held in an s, p, d and f orbital: 2, 6, 10 and 14. These numbers also match perfectly with the periodicity seen in the periodic table.

Electron Configuration

The only remotely difficult MCAT question you'll face regarding electron configuration is to provide the configuration for cations and anions. For cations, move back one box in the periodic table for each electron missing. For anions, move forward one box for each extra electron. - "most stable" electron configuration= the element in its ground state

The Bohr Model of an Atom

The original Bohr model was that of a small, positively charged nucleus surrounded by very small negatively-charged electrons that orbit the nucleus in defined planetary-like orbits. -A small round nucleus containing protons and neutrons, surrounded by electron "shells" of increasing size (the shells resembling the rings of a target). -two electrons fit in the first shell, followed by eight in the next shell and in each shell thereafter until all electrons for that atom are assigned

How many more neutrons are there than electrons in 54Fe+?

The superscript next to any element gives the mass number, which is the sum of the protons and neutrons. The position in the periodic table, #26 in this case, gives the atomic number, or number of protons. Thus, 54Fe has 26 protons and 28 neutrons. Because there is a charge of +1, there must be one less electron than there are protons, or 25 electrons. There are thus 3 MORE neutrons than electrons.

Enzyme vs. Catalyst

The word catalyst is a more general term for any substance that increases the rate of a reaction without being altered or consumed during the process. -An enzyme is one type of biological catalyst. Enzymes are long protein chains folded into complex tertiary structures that feature an active site that is unusually specific to the reactants and/or transition state of the reaction it catalyzes. -The order of amino acids in the protein and the folding of the protein are such that the active site has a very specific contour and layout—with complementary shapes and electrostatic regions that stabilize the transition state of the reaction and thereby lower the energy of activation. -It could be said that all enzymes are catalysts, but there are many catalysts that are not enzymes. In fact, the catalysts you will encounter in general chemistry are almost always inorganic compounds or solid metals.

Theoretical yield

Theoretical yield is the amount of product in grams that would be produced if the reaction ran 100% to completion. In other words, you take your limiting reagent, do a mole-to-mole conversion to get moles of product, and then convert that to grams. This is your theoretical yield

Solving Half-Life Problems

There are three variables involved in half-life problems: half-life, t1/2, time elapsed, t, and the amount of the substance in grams, g. You are usually given two of those three and asked to solve for the third. Try to do this conceptually in your head—do not use a formula. -Another question may give you the initial and final mass of the substance plus the amount of time elapsed, and ask you to calculate the half-life. In such a case, first decide how many times the substance had to be cut in half to go from the initial value to the final value (i.e., the number of half-lives). Divide the total time elapsed by the number of half-lives to get the length of each half-life. -Always take notes when counting half-lives. Many students make silly errors because they miscalculate the number of half-lives. Write it down and you won't mess up!

When a solution of FeCO3 and water is mixed with HBr, a gas is produced. This gas is most likely:

To help you solve this problem, write out the reactants. You have Fe2+ with water, CO32- and HBr. -Using a little O-Chem knowledge will help you here even though this would show up on the PS section. -The oxygens on the carbonate would make good nucleophiles and the H on the HBr a good electrophile. -To know you've figured out what is actually happening on one of these "which gas is produced" questions, you usually need to be able to account for what happens to each species. -First, you will learn in the O-Chem section that decarboxylation, the forming of CO2, is a very energetically favorable reaction. -If one of the oxygens on carbonate gained two H's from two HBr molecules, water could leave and CO2 would be formed. -The iron and bromine ions could then combine, which sounds logical because you've probably seen FeBr2 before. -That accounts for all the species in a logical way and that happens to be exactly what occurs. In general, all acids react with metal carbonates to form CO2 and the related salt

Naming Transition Metals

When written in words, compounds that include transition elements must have a roman numeral showing the oxidation state of the metal Ex: iron(II)sulfate iron(III)sulfate).

What would happen if you changed the conditions by increasing the temperature?

When you see exothermic (indicated by a -∆H or because they tell you it "evolves heat," raises the temperature of the reaction vessel, or something similar) IMMEDIATELY write out the reaction on your scratch paper and place a ∆ (delta) on the right side of the equation, signifying heat as a product. If the reaction is endothermic, put the delta on the left side, signifying heat as a reactant. Next, treat the delta symbol like any other reactant or product. Raising the temperature is like adding more of it, and lowering the temp is like taking some of it out.

Few limited things in chemistry that can cause light emission and/or color changes

Whenever photons of light are emitted from an atom it has to be because electrons are relaxing from a higher to a lower energy level and releasing the extra energy as photons. -A somewhat different thing can happen with transition metals. They have partially filled d orbitals that allow for electrons to absorb many different wavelengths of light. -Usually, they will absorb nearly all of the white light, EXCEPT for a few wavelengths, resulting in a dull to rich color, most often blue or green (although other colors are seen). -This color is NOT the result of light being emitted, but the result of the few wavelengths of UNABSORBED light being reflected. -Very bright colors that are fluorescent, phosphorescent, or that show up in things like flame tests, are usually due to actual photon emission rather than reflection of unabsorbed light. -The duller colors seen in solution chemistry are almost always the later kind, due to partially filled d orbitals in transition metals. *at higher ionization energies, the energy provided by the flame may not have been sufficient to excite the electrons.

Limited Reagent

You must have a balanced equation. -You must convert to moles first. -Compare the number of moles you have to the number of moles required to run one cycle of the reaction, as indicated by the coefficients. -The reactant you will run out of first is the limiting reagent. -The reactant you have the least of, in either grams or moles, is NOT necessarily your limiting reagent. For example, suppose for the combustion of methane you have 1.5 moles of O2 and only 1.0 mole of methane. -Because you need two moles of O2 to react with one mole of methane, you will run out of O2 first and it is therefore your limiting reagent—even though you have more moles of O2 than you do methane. -When asked which species will require the most oxygen to combust, you must first make sure it is combustible. Most gases and all hydrocarbons are combustible. Water is never combustible. After that, make a ranking system in which you assign a +1 for each carbon contained in a compound and a -0.5 for each oxygen in a compound.

Moles of Oxygen Needed for Combustion

You will occasionally be asked to predict the species that will require the most oxygen to combust. -Here is a simple ranking system to make such predictions quickly: -*Add 1.0 for each carbon* - *subtract 0.5 for each oxygen* The higher the resulting number the more oxygen necessary for full combustion. This is NOT, however, the actual number of moles required—this is only a ranking system. The only way to determine the exact moles of oxygen required for a combustion reaction is to write out and balance the combustion equation.

Element Symbols

Z=atomic number (i.e.,the number of protons) A=mass number (i.e.,the number of protons + the number of neutrons)

Zero Order Reactant

[A] vs. time is linear (i.e., yields a straight line) with slope = -k For a zero order reaction, rate = k (k = - slope of line)

Second Quantum Number

a.k.a. "l" or "the azimuthal quantum number" or "the angular momentum quantum number" o -Gives the subshell or orbital; has values of 0, 1, 2 or 3, and from this we know the shape: 0=s;1=p;2=d;3=f

Fourth Quantum Number

a.k.a. "ms" or "the electron spin quantum number" -Gives the spin, which is either +1⁄2 or -1⁄2. Positive spin is represented by an up arrow in an electron configuration diagram and negative spin is represented by a down arrow.

THINK OF NEUTRONS AS

neutron= proton+ electron

Coordination Complex

the product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coordinate covalent bonds. *If a molecule does not have a lone pair of electrons it CANNOT form coordinate covalent bonds with metals or other Lewis acids* -Ligands are Lewis bases - they contain at least one pair of electrons to donate to a metal atom/ion. Ligands are also called complexing agents. -Metal atoms/ions are Lewis acids - they can accept pairs of electrons from Lewis bases. *metals with unfilled d orbitals do not have to obey the octet rule * -Within a ligand, the atom that is directly bonded to the metal atom/ion is called the donor atom. -A coordinate covalent bond is a covalent bond in which one atom (i.e., the donor atom) supplies both electrons. -This type of bonding is different from a normal covalent bond in which each atom supplies one electron. -If the coordination complex carries a net charge, the complex is called a complex ion. Compounds that contain a coordination complex are called coordination compounds. -This usually occurs between a transition metal with a positive oxidation state and an atom containing a lone pair. Multiple NH3 molecules bonded to a transition metal is probably the most common example you will encounter [e.g., Co(NH3)42+]

Kinetics

the study of reaction rate. In other words, how quickly the reaction proceeds. This is usually measured in terms of how fast the reactants disappear by tracking changes in the concentration of the reactants as a function of time (i.e., Molarity/second ; M/s). -think of rate as depending on how fast the reactant molecules are moving (how much KE they have) and the relative height of the Energy of Activation "hill" that they must surmount in order to turn into products. -The reactant molecules must also collide with the right orientation to one another. -At any given time molecules in the mixture of reactants will have a variety of different energies. -Some will have enough to react while others will not. Because temperature is a measure of the average KE of the molecules, increasing temperature will cause a greater fraction of the molecules to have sufficient energy to overcome the barrier and therefore more of them will react. -It is fairly straightforward to imagine that if only a tiny fraction of the reactants have enough energy to get over the hill, a very long time must pass before all of the reactants—just a few at a time—make it over the hill. -By contrast, if the average energy of the reactants is very close to the energy of activation, then a greater percentage of them will exceed that threshold and it will take far less time for most of the reactant molecules to make it over the hill. -Further, if the reactants have more KE (higher temperature) they will be moving more quickly and collide more often, increasing the probability two reactants will strike one another with the correct orientation needed to react. -Things they should associate with kinetics include: rate, catalysts, enzymes, energy of activation, reaction order, and transition state. - Temperature is the IMPORTANT exception because it traverses the "wall of separation" and impacts both thermodynamics and kinetics. Increased temperature increases the rate of the reaction. Increased temperature can either increase or decrease the Keq depending on whether the reaction is exothermic or endothermic (we'll discuss this in more detail later). Drill into your head that "temperature is the only thing that changes Keq."

Thermodynamics

thermodynamics of a reaction reflect the potential reactivity (for example, given infinite reaction time) and includes all measurements of energy flow and relative stability. -Thermodynamics produces the quantities ∆H, ∆G, ∆S, Keq and so forth. -A simple, but effective conceptual approach to thermodynamics is to think of it as differences in energy across a reaction. -If the bond energies of the reactants are lower than the bond energies of the products, then the products are by definition more stable. -We would expect therefore, that as the molecules transform from a less stable state to a more stable state there would be a release of energy (i.e., an exothermic process). -If the reverse is true we would expect that energy would be required (i.e., endothermic) to drive the molecules from a more stable state (higher BE) to a less stable state (lower BE). -Entropy works in a similar way, but it is a measure of randomness or disorder and has the units of energy/temperature (J/K). -It requires energy to create order. Conversely, there is an energy release associated with going from a more ordered state to a less ordered state -Gibbs free energy combines these concepts and represents the total free, available energy either produced or required by a reaction as a function of BOTH -changes in the bond energies (∆H) -and changes in the entropy state (∆S). -Those are good conceptual starting points for both kinetics and thermodynamics. -Things they should associate with thermodynamics include: Keq, Q, entropy, enthalpy, Gibbs free energy, "favorability," "spontaneity," "differences in energy between products vs. reactants," and yield - Temperature is the IMPORTANT exception because it traverses the "wall of separation" and impacts both thermodynamics and kinetics. Increased temperature increases the rate of the reaction. Increased temperature can either increase or decrease the Keq depending on whether the reaction is exothermic or endothermic (we'll discuss this in more detail later). Drill into your head that "temperature is the only thing that changes Keq."

Derive a related equation that would allow you to calculate the energy of a photon knowing only velocity and wavelength.

v = f for f to get: f = v/λ). Substitute this for frequency in the above equation to get E = hv/λ), often written as E = hc/λ)