CHEM 1

Bond Energy

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. ATP- highly unstable= low energy bonds H2- Highly stable- high energy BONDS 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. ATP is high energy, thus highly unstable Bond energy is a measure of the strength of a chemical bond. The larger the bond energy, the stronger the bond HIGH ENERGY MOLECULE= LOW ENERGY BOND LOW ENERGY MOLECULE= HIGH ENERGY BOND

p-block

the p-block is the set of six columns starting with boron and ending with neon

The Law of Mass Action

o Keq = [products]x/[reactants]y -the molarity values are the exponents... o Keq is written with every term raised to an exponent equal to its coefficient in the balanced equation (remember, however, that you do NOT do this when writing rate laws). Pure liquids (ℓ) and pure solids (s) are never included! Usually done in molarity, which moles/Liters How does each of the following affect equilibrium: addition of a catalyst- Does nothing to equilibirum increased temperature-exo rxn decrease Keq and endo rxn increase Keq, lowering the Ea-Lowering energy of activation impacts rate, NOT equilibrium stabilizing the transition state- same thing as EA addition of reactants/products- Does nothing to equilibirum, "temperature is the only thing that changes Keq."

Pauli Exclusion Principle

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.

d-block

the d-block is the entire set of transition metals in the middle of the table

Alkali Metals

1A to the far left

Alkaline Earth Metals

2A just to the right of Alkali metals

Coordinate Covalent Bonds

: A covalent bond in which both electrons shared in the bond are donated by one atom. In most cases, more than one of these "donor" molecules surround and bind a single "recipient" molecule. The donor molecule must have a lone pair and the recipient molecule must have an empty orbital. ***If a molecule does not have a lone pair of electrons it CANNOT form coordinate covalent bonds with metals or other Lewis acids. The complex formed by the metal and the molecules forming coordinate covalent bonds with that metal, is called a "coordination complex." it typically happens when an atom donates it's electrons to the d the empy d orbital of another atom

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. 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.

Double Displacement (Metathesis reaction)

A double displacement reaction, also known as a double replacement reaction or metathesis reaction, is a type of reaction that occurs when the cations and anions switch between two reactants to form new products.

Important Terminology Regarding Covalent Bonds:

BOnd length, bond energy, bond dissociation energy, heat of combustion

Cyanide

CN-

Carbonate

CO3^2-

Use a rxn 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.

Cations vs Anions

Cation- atom with fewer electrons than protons Anion- Any atom that has more electrons than protons Metals form Cations but non metals form anions Cations are smaller than their neutral counterpart and anions are larger than their neutral counterpart This size difference between anions, cations, and neutral atoms is due to the following: Cations are smaller because the relative charge in the electron cloud and nucleus increase by 1 unit, causing the electron cloud to suck in. Another reason on the differences in size is due to the fact that most cations form due to losing electrons to match electron configuration of nearest noble glass. This means they lose an entire shell and therefore volume. Anions are larger because those additional electrons take up additional space in the electron cloud, and repel one another, thus making electrons larger.

Nitrite

Formula: NO2-

Fourth Quantum Number

Fourth Quantum Number: a.k.a. "ms" or "the electron spin quantum number" Gives the spin, which is either +½ or -½. Positive spin is represented by an up arrow in an electron configuration diagram and negative spin is represented by a down arrow. Electrons can "spin" two possible ways, thus two possible values So there is ms= +½, which is spin up and ms=-½, which is spin down.

Gamma Emission

Gamma rays are usually emitted as a byproduct of the types of decay outlined above. Gamma decay does not change the number of nucleons!

Inorganic Nomenclature

General Ionic Compunds: Name the cation first, then the anion (i.e., calcium sulfate is CaSO4, not SO4Ca, and is not called "sulfate calcium") Transition Metals: When written in words, compounds that include transition elements must have a roman numeral showing the oxidation state of the metal (e.g., iron(II)sulfate vs. iron(III)sulfate) Monatomic Ions: Named by replacing the last syllable with "-ide." (e.g., sulfide ion, hydride ion, chloride ion, etc. 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. 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.

Ionization Energy

Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Conceptually, ionization energy is the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation. Generally, elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled. Elements on the left side of the periodic table have low ionization energies because of their willingness to lose electrons and become cations. Thus, ionization energy increases from left to right on the periodic table. Another factor that affects ionization energy is electron shielding. Electron shielding describes the ability of an atom's inner electrons to shield its positively-charged nucleus from its valence electrons. When moving to the right of a period, the number of electrons increases and the strength of shielding increases. As a result, it is easier for valence shell electrons to ionize, and thus the ionization energy decreases down a group.

Ammonia

NH3

Ammonium

NH4+

Nitrate

NO3-

Hydroxide

OH-

Oxidation and Reduction

Oxidation- Loses Electrons, Loses H+ REduction- Gains electrons, gains H+ oil rig or leo ger

Phosphate

PO4^3-

Calculating Percent Mass:

Percent Mass = (mass of one element/total mass of the compound)(100%) Q20. What is the percent mass of carbon in glucose? What is the percent mass of hydrogen in water? The total MW of glucose is 180g. The weight of the six carbon atoms in glucose is 72g. Therefore, 72/180*100 = 40%. The total mass of water is 18g. The mass of the two hydrogen atoms is 2g. Therefore, 2/18*100 = 11%.

First Quantum Number

Principle Quantum Number n It gives the shell, valence e= are in outermost shell, and represents the relative energy of electrons in that shell Tells us the main energy level or the type of shell it is in As n increases, a higher energy level is associated it, example n=2 > n=1

Electron Configuration

Electron configurations are a list of quantum numbers and the number of electrons in each Energy level diagrams are the stair-step diagrams you drew in general chemistry with lines representing orbitals and up and down arrows representing electrons Orbitals are filled from low to high, always in order, so 1st to 2s, so on and so forth example- Carbon- 1s^2,2s^2,2p^2 hydrogen- 1s^1, Helium is 1s^2 Li- 1s^2, 2s^1 N=1s^2,2s^2,2p^3 Si=1s^2, 2s^2, 2p^6, 3s^2, 3p^2 NOble gas config example- Si=1s^2, 2s^2, 2p^6, 3s^2, 3p^2= [Ne] 3s^23p^2 Ni=1s^2,2s^2,2p^6,3s^2,3p^6, 4s^2, 3d^8: noble gas config= [Ar] 4s^2, 3d^8 -The 4s^2 is the valence electrons... 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. Ca^2+= [Ar] For anions, move forward one box for each extra electron.

Energy Levels

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. The need more energy when they go higher in steps, when they then leave down the state, they show a color Ground state is most stable state of atom, excited state is any state other than the ground state of an atom. Electrons in atoms can only change to discrete energy levels

Examples of Nomeclature

Fe2O3= Iron (II) Oxide Ammonium Nitrate- NH4NH3 MgCl2- Magnesium Chloride Sodium Bicarbonate-NaHCO3 CaCO3= Calcium Carbonate Mercury (II) Sulfide= Hg2S Good practice sites: http://www.wbu.edu/academics/schools/math_and_science/chemistry/resources/inonomen/quiz.htm http://chem.libretexts.org/Core/Inorganic_Chemistry/Chemical_Compounds/Nomenclature_of_Inorganic_Compounds

How to fill electron orbitals

Make sure students are familiar with the traditional order of 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, 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

Metals vs Non Metals

Metals: larger atoms, loosely held electrons, more likely to lose electrons form positive ions. Lustrous, ductile, malleable, conductors of heat and electricity. Ionic bonds with non metals Non-metals: smaller atoms with tightly held electrons. Nonmetals "like" to gain electrons and form negative ions. They have lower melting points than metals, and form covalent bonds with non-metals.

Permangate

MnO4-

Manganate

MnO4^2-

Moles of Oxygen Needed for COmbustion

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 and 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.

Collisions cause Reactions to Occur

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 o Rate is measured as the change in molarity (M) of the reactants per second (M/s) How does the following affect reaction rate: Reactants- Increases rxn rate as long as reactants are in rate law Products- no effect Catalysts- Increase rate Energy of Activation- decreases reactions at constant temp. Energy of Transition State-decreases reactions at constant temp Energy of the reactants- Closer to Ea, thus increasing rxn rate Temperature-Increase KE, thus increasing rxn rate

Atomic Radius

Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. 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.

Avogadro's number

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. You can have a mole of atoms, molecules, cars, monkeys, whatever

The Reaction Quotient

The Equilibrium Constant can only be calculated at equilibrium. The reaction quotient Q is defined as the ratio of the concentration of the reacting species at any point of time other than the equilibrium stage. 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. o If Q > K, the reaction will proceed to the left or reactants. o If Q < K, the reaction will proceed to the right or products. 1) Nature of reactants and products taking part in the reaction 2) Temperature 3) Stoichiometry of the equilibrium reaction

Atomic Weight

The average mass, measured in amu, of all the isotopes of a given element as they occur naturally. Atomic weight (actually a mass; it cannot be a weight because it is not multiplied by gravity) is usually defined as the mass of one mole of any atom. however, just think of atomic weight/molar mass/molecular weight as the "g/mol" measurement given in the periodic table for individual elements, or in the case of molecular weight, the sum of those measurements for all of the atoms in a molecule. It is the number you will use to convert grams of any substance into moles

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 Mass accounts for protons

Q38. Why can you usually ignore the rate law for the uncatalyzed reaction?

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.

Lanthanides

The upper row in the f-block

Periodic Table Trends

Size Matters, families are similar, Zeffective Size Matters refers to the trend that is depend on atomic size. Smaller atom's nuclei are closer to their valence electrons and are held more tightyl to positively charged nucleus. Greater force causes atoms to be more electronegative, having higher ionizatione nergy, greater electron affinity, and less metallic character than a larger atom. Larger atoms are better at stabilizing charges, don't form pi bonds and have d orbitals where they can house extra electrons. They won't form pi bonds because they are weak due to decrease in overlap of p orbitals Families are elements in the same column that have similar properties chemically and physically, like SiH4 is similar to CH4

Decomposition Reaction

a reaction in which a single compound breaks down to form two or more simpler substances

Combination Reaction

also known as a synthesis reaction in chemistry is when two or more substances, or reactants, combine with each other to form a new product. The product will always be a compound.

Electron Orbitals

an orbital equates to a room and each room has two beds to be occupied by a maximum of two persons/electrons. There is only one room in an s subshell (studio apartment) and it can hold two electrons. There are three bedrooms in a p subshell and each bedroom can hold two electrons for a total of six. There are five bedrooms in a d subshell and each bedroom can hold two electrons for a total of ten. There are seven bedrooms in an f subshell and each bedroom can hold two electrons for a total of fourteen. Much like teenagers, electrons do NOT like to share rooms. Therefore, they will always fill empty orbitals first and only pair up inside the same orbital once it becomes necessary.

Rates of Multi-Step Reactions:

o If there is a slow step, the slow step always determines the rate. o If the slow step is first, the rate law can be written as if it were the only step. o 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.

First Order

ln[A] vs. time is linear with slope =-k A first order reaction depends on the concentration of only one reactant (a unimolecular reaction). Other reactants can be present, but each will be zero order. The rate law for a reaction that is first order with respect to a reactant A. It is only linear if it is the ONLY REACTANT or IF ONLY ONE REACTANT MATTERS. If it is non linear, it means it isn't first order

Bicarbonate

HCO3-

Actinides

actinides are the lower row in f- block

Electron Capture

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

Positron Emission

A proton is changed into a neutron, with expulsion of a positron. We are doingP+N and P-1, we are reducing a number of protons. similar to electron capture

What increases or decreases as you go across a period or down a group of the period table

Atomic size decreases going across the table or up any column. Fluorine is the smallest atom, except for hydrogen and helium (the noble gases are actually larger in size than the group 7A elements). From this we can intuit anything Electron Affinity: greatest for the smallest atom and least for the largest atom. Electronegativity: greatest for the smallest atom and least for the largest atom. Ionization Energy: very small for a very large atom and larger for a smaller atom Atomic Radius: Atomic size decreases going across the table or up any column Metallic Character: Metallic character will increase with the size of the atom do NOT want students to memorize these trends. ONLY to learn the patterns for changes in atomic radius and then use intuition to quickly determine the pattern for whatever characteristic they are evaluating.

s-block

the s-block is the first two columns

Second Order

1/[A] vs. time is linear with slope = k A second order reaction depends on the concentrations of one second order reactant, or two first order reactants.

Bond Length

distance between the nuclei of the atoms forming the bond the shorter the bondlength, the higher the bond energy, more stability, thus more energy

Sulfate

SO4^2-

Second Quantum Number

"ℓ" or "the azimuthal quantum number" or "the angular momentum quantum number" ℓ n-1= # of subshells 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 The shape of the orbital, ℓ can equal 0, 1, 2, -1, so when n=1, ℓ=0, this refers to s orbital that is shaped as a sphere n=2, ℓ=0,1 thus we have 2 allowed values, so when ℓ is equal to 0, we get a sphere, if ℓ=1, then we get a p orbital (dumbell)

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) Zero Order, First Order, Second Order. Something is ONLY LINEAR when there is ONE reactant, and it's the only one that has an effect.

Bond Dissociation Energy

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

Bonding and Anti-Bonding Orbitals:

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.

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. THE MCAT WILL GO YOU UNBALANCED REACTIONS..

Deriving a formula from percent mass

1) Change the percent mass for each element into grams (i.e., 15% = 15g), always do it out of 100g, its the easiest 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. 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). 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: XY = 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.

Catalysts:

A catalyst is any substance that increases reaction rate without itself being consumed in the process. 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. What do catalysts change?-They don't change Ea, but provide an alternate route that has a lower Ea What do they not change? -They do NOT change the equilibrium, Keq, enthalpy change, entropy change, Gibbs free energy, or any other thermodynamic properties.

Beta Decay

A neutron is changed into a proton with the ejection of an electron. The neutron is changed to a proton to help keep it at the correct atomic mass number. THat is why the neutron converts to a proton

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. IN ORDER FOR THE ELECTRON TO BE FREED FROM THE NUCLEUS, IT NEEDS TO BE HIT WITH ENOUGH ENERGY THAT IS NOT ONLY EQUAL TO THE ELECTRON ENERGY LEVEL, BUT MUST BE IN EXCESS FOR TEH ELECTRON TO BE FREED. IT'S ALL ABOUT USING ENOUGH ENERGY FOR THE DIFFERENCE BETWEEN 2 ENERGY LEVELS, AND WHEN IT DOES HAPPEN, A PHOTON IS SHOT OUT WITH ENERGY REPRESENTING THAT DIFFERENCE.

The Work Function in Energy Levels

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

ClO-

Chlorite

ClO2-

Chlorate

ClO3-

Perchlorate

ClO4-

Reaction Types:

Combination Decomposition Single Displacement Double Displacement (a.k.a. "metathesis reaction")

Good vs. Poor Electrolytes

Covalent compounds that dissociate 100% in water, such as strong acids and strong bases, make good electrolytes. Strong Acids, strong bases Other covalent compounds are usually poor electrolytes. Ionic compounds that are soluble in water always make good electrolytes Salts

Covalent vs. Ionic:

Covalent: 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. ex- HCl, CO2 Ionic: Ionic bonds are usually formed a between a metal and a non-metal and are due to an electrostatic attraction ex- NaCl, cation + anion, solid at room tempreature 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 (Clin this case) pulled one electron completely away from sodium. This would result in essentially the same result, a sodium cation and a chloride anion

E=hf

E- Energy of a photon h= Plank's constant f=frequency v = f (lambda), f=v/lambda, which you can then plug into the energy equation for E=hv/lambda

Electronegativity

Electronegativity can be understood as a chemical property describing an atom's ability to attract and bind with electrons From left to right across a period of elements, electronegativity increases. If the valence shell of an atom is less than half full, it requires less energy to lose an electron than to gain one. Conversely, if the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one. Electronegativity measures an atom's tendency to attract and form bonds with electrons. This property exists due to the electronic configuration of atoms. . Because elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared with the energy required to lose electrons. As a result, the elements on the left side of the periodic table generally lose electrons when forming bonds. Conversely, elements on the right side of the periodic table are more energy-efficient in gaining electrons to create a complete valence shell of 8 electrons. The nature of electronegativity is effectively described thus: the more inclined an atom is to gain electrons, the more likely that atom will pull electrons toward itself.

Empirical vs Molecular Formula

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.

Equilibrium

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 Equilibirum is the rate going in the forward direction is the equal in the rate going backwards, but this doesn't mean the concentrations are the same, it just means concentrations wont' change anymore When a chemical reaction has attained the equilibrium state, the concentrations of reactants and products remain constant over time, and there are no visible changes in the system. However, there is much activity at the molecular level as the reactant molecules continue to form product molecules while product molecules react to yield reactant molecules. Chemical equilibrium is achieved when the rates of the forward and reverse reaction are equal and the concentrations of the reactants and products remain constant 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 Students frequently confuse equilibrium with rate. For many students it seems intuitive (BUT IS ABSOLUTELY WRONG) that if a reaction has a large Keq this means the reaction "really wants" to reach equilibrium and will therefore proceed toward it quickly. You should be drilling into your students the conviction that equilibrium and reaction rate describe totally different things. Many reactions have high Keq values, but proceed very, very slowly. 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. 1) At equilibrium, the rate of the forward reaction is equal to the rate of the backward reaction. 2) Since both reactions take place at the same rate, the relative amounts of the reactants and products present at equilibrium will not change with time. 3) The equilibrium is dynamic, i.e., the reactions do not cease. Both the forward and reverse reactions continue to take place, although at equal rates. 4) A catalyst does not alter the position of equilibrium. It accelerates both the forward and backward reactions to the same extent and so the state of

Quantum Mechanics

Every electron in an atom has a unique "address" or "location." Electron addresses consist of four numbers. One could think of the first number as giving the street name (i.e., shell), the second as giving the house or apartment (i.e., subshell), and the third as giving the room within that apartment (i.e., orbital). Electrons can come in pairs, with two electrons sharing one orbital. They are like two siblings sharing the same room. They are differentiated by their "spin." Quantum numbers 1, 2, 3, and 4 n, orbitals, # electrons in orbital, #electrons in shell so n=1, then ℓ=0, which there is 1 s orbital, and mℓ=0, and the fourth quantum number there are 2 max electrosn in 1s, and 2 electrons in the shell (2n^2) If n=2, ℓ=0,1 thus have 1 s orbital, mℓ= -1,0,+1, thus 3 different orientations, 3 different p orbitals, 2 electrons in 1s, and 6 electrons in 3p orbitals, and thus (2*2^2)=8 electrons in the shell n=3, ℓ=0,1,2, thus 1s, 3p, and 5d orbitals, mℓ= -2,-1,0,+1,+2=5 d orbitals, thus we have 18 electrons--------------------The three quantum numbers (n, l, and m) that describe an orbital are integers: 0, 1, 2, 3. The principal quantum number (n) cannot be zero. The allowed values of n are therefore 1, 2, 3, 4... The angular quantum number (l) can be any integer between 0 and n - 1.If n = 3, l can be either 0, 1, or 2. The magnetic quantum number (m) can be any integer between -l and +l.If l = 2, m can be -2, -1, 0, +1, or +2. Orbitals that have same value of principal quantum number form a Shell(n). Orbitals within the shells are divided into subshell (l)s:l = 0 p:l = 1 d:l = 2 f:l = 3

Q34. For a reaction with two reactants, A and B, a graph of ln[A] vs. time is linear. How many of the following statements are true? 1) Reactant A must be first order, 2) Reactant B could be first order, 3) Reactant B cannot be impacting rate, 4) Reactant B must be in excess.

Getting a positive result (i.e., a line for one of the graphs) gives us much more information. Because the graph of ln[A] is linear we know that statement 1 is true, reactant A is indeed first order. We also know, however, that no other reactants are impacting rate. Statement 2 is NOT known. Reactant B could be first order; however, if it is first order then we know it MUST be in excess because only reactant A is impacting rate. Reactant B could also not be first order. It could be zero order and not impacting rate at all—an alternative explanation for why only reactant A is impacting rate. Statement 3 is known for this exact moment and set of conditions. Reactant B cannot be impacting the rate; if it were, the graph of ln[A] would not have been linear. Statement 4 is NOT known but could be true. We know that reactant B is not impacting rate, but that could be either because it is in excess or because it is zero order.

halogens

Halogens are the group 7A elements just to the left of the noble gases

Kinetics

Kinetics is the study of reaction rate. 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. 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 It is IMPERATIVE that students understand that the rate of a reaction is independent of its thermodynamic properties. It is trying to confuse you with the fact that solids and liquids are always left out of the formula for the equilibrium constant (Keq).

Writing Rate Laws:

Know how to write a rate law, how to determine one from a table of experimental values, 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). o Rate Law Exponents: Students often get the false idea that the exponents in the rate law are given by the coefficients in the balanced equation. 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. For the MCAT, always assume that they do NOT. TEMPERATURE MATTERS, if temprature is given, you can only get a rate law from concentrations that have similar tempreature.

R=K[A]^x[B]^y

R = Rate of rxn K= rate constant Orders determined experimentally by data. [A]^x= [B]^y= Overall order =3 https://www.khanacademy.org/science/chemistry/chem-kinetics/reaction-rates/v/rate-law-and-reaction-order

Radioactive Decay & Half Life

Radioactive decay is 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 With the different types of DECAY- THINK OF NEUTRONS AS: neutron = a proton + an electron THINK OF PROTONS AS: proton = neutron + a positron

Bohr Model of An Atom

Size of Components: A nucleus is made up of protons and neutrons held together by a strong residual force. Protons are positively charged, neutrons neutural, and about same size and mass. Electrons are much smaller, to the point that the electron cloud is mostly dead space. Charges: Protons are +, neutrons are neutral, electrons are - 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. 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 have both wave like and particle like nature, similar to light Electrons do not orbit the uncleus in circular patterns like rings Electrons have S, p d, and f orbitals with unique shapes

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. When you disrupt the equilibrium, creating a "shift" according to Le Chatelier's principle, what happens to Keq? Does it change? -Keq doesn't change, the value of equilibirum constant for the rxn does not change. Predict the effects of doing each of the following to a reaction at equilibrium: 1) adding/removing reactants- adding shifts right/ removing shifts left 2) adding/removing products- Adding shifts left, removing shifts right 3) increasing/decreasing pressure- Increasing pressure shift rxn to side with fewer moles of gas, decreasing pressure shift rxn toward side with more moles of gas 4) increasing/decreasing temperature.- Increasing temp changes Keq and shifts the rxn: -exothermic increase temp shift rxn to left and Keq decreases -endothermic rxn increasing temperature, shifts to the right and Keq increase -decreasing temp will have the exact opposite for each.

Group/family

THe Vertical column

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. (look at metallic character, more metallic character, it's a better conductor... ALWAYS COMPARING TO SODIUM CHLORIDE Q16. What is the expected condosity of a 3.0 M 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.

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

The "overall order" of a reaction = the sum of the exponents in the rate law

Period

The HOrizontal row

Heisenberg Uncertainity

The Heisenberg Uncertainty Principles states that the more we know about an electron's position, x, the less we know about its momentum, p.

Molar mass

The mass in grams of 1 mol of a substance.

Metallic Character

The metallic character of an element can be defined as how readily an atom can lose an electron. From right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, enabling an easier loss of electrons. Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer shells are farther away. The principle quantum number increases and average electron density moves farther from nucleus. The electrons of the valence shell have less attraction to the nucleus and, as a result, can lose electrons more readily. This causes an increase in metallic character.

. For a reaction with two reactants, A and B, a graph of 1/[A] vs. time is non-linear. Which of the following is known? 1) The reaction cannot be second order in A and independent of B, 2) Reactant B must be involved in the rate law, 3) Reactant B cannot be in excess.

The observation that a graph of 1/[A] is non-linear is somewhat inconclusive. The graph could have been non-linear because both reactants are impacting the rate (violating the rule that these graphs will only be linear if only one reactant species is impacting rate). However, it could also be non-linear if reactant A is the only reactant impacting rate, but reactant A is not second order. For example, suppose that reactant A is actually first order; the graph of 1/[A] would not be linear, but the graph of ln[A] would be. Statement 1 is the best choice because if reactant A was second order and reactant B did not impact rate, we would expect a linear plot. Statement 2 is NOT known. Reactant B could be in the rate law and that is why the graph is not linear; however, it is equally plausible that reactant B is NOT in the rate law and the graph of 1/[A] is not linear because A is first order, not second order. Statement 3 is NOT known either. As we have already explained, the graph could be linear either way. If reactant B is in excess then the graph could be non-linear because reactant A is actually first order, not second order. If reactant B is not in excess (and is in the rate law) then the graph could be non-linear because both A and B are impacting rate.

Molecular Weight

The sum of an atomic weight of a molecule's component atoms

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 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. Some texts define "catalyst" as being inorganic molecules that catalyze reactions, and enzymes as being organic molecules that catalyze reactions. However, because an enzyme is still "catalyzing" a reaction, we think the use of the term "catalyst" as a more categorical term makes the most sense.

Theoretical Yield

Theoretical Yield: 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. 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 Percent Yield: The percent yield is just the ratio of the actual yield over the theoretical yield multiplied by 100. Remember that yield is a function of reactants and equilibrium, NOT rate, FOCUS ON THESE TWO WAYS TO INCREASE YIELD: 1) Start with more reactants 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. CAVEATS: Action 1) above 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. 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: o Add 1.0 for each carbon and 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.

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. For example, one question may tell you that we currently have 500 g of element Z, and that the half-life of element Z is 10 years. It then asks how much of element Z will remain 40 years from now. The half-life tells us that every 10 years the substance is cut in half. Thus, in 40 years it will be cut in half four times. Write 500 g on your scratch paper, then cut it in half four times to get the correct answer: 31.25 g. 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! This is yet another application of the Altius mantra: Write it Down and Draw it Out!

Equilibrium Constant

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).

Q35. Describe how you could use the rate order graphs to determine the order of each reactant in a multi-reactant reaction experimentally in the lab: What would you need to measure? What would you do with the data?

To determine the order of each reactant experimentally you would only need to ensure that all other reactants were in excess and measure the concentration of the limiting reactant as a function of time. You would then use the measured concentration of the reactant in question in each of the types of graphs. If all other reactants are in excess, one of these graphs should be linear. You may be tempted to think that you wouldn't get a positive result if the reactant you were testing was NOT impacting rate. However, that would produce a line for [A] vs. time (i.e., the reaction would zero order in that species). Remember that zero order reactants are not included in the rate law!

Transition Metals

Transition metals are the elements in the four middle rows

Mole-to-mole Conversion:

We have found that students perform much better on these problems if they have a map already in their head of where they can go. We do not want you to memorize the flowchart shown below. However, if you can internalize it naturally you will always be able to plan out exactly how to move from what you are given to what you need to calculate

Activation Energy (Ea)

You can think of the activation energy as a barrier to the reaction. Only those collisions which have energies equal to or greater than the activation energy result in a reaction. Remember that for a reaction to happen, particles must collide with energies equal to or greater than the activation energy for the reaction

The Atom

Z= Atomic number, the number of protons, this is what defines an element A= mass number, which is protons + neutrons

Zero Order

[A] vs. time is linear (i.e., yields a straight line) with slope = -k zero order is not included in the rate law, so if [A]^0, then the rate law would only be be shown as R=K Putting it in excess makes it effectively zero order under those conditions and any effect remaining must be due solely to only ONE reactant

Single Displacement Reaction

a type of oxidation-reduction chemical reaction when an element or ion moves out of one compound and into another-that is, one element is replaced by another in a compound.

f-block

d the f-block is the lanthanides and actinides which actually occur in order between the s-block and d-block elements on rows 6 and 7 respectively.

Isotopes

each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element. Isotopes of an element will contain the same number of protons and electrons but will differ in the number of neutrons they contain. In other words, isotopes have the same atomic number because they are the same element but have a different atomic mass because they contain a different number of neutrons 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). For example, carbon is normally present in the atmosphere in the form of gases like carbon dioxide, and it exists in three isotopic forms: carbon-12 and carbon-13, which are stable, and carbon-14, which is radioactive.

Electron Affinity

electron affinity is the ability of an atom to accept an electron Electron affinity generally decreases down a group of elements because each atom is larger than the atom above it With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker. Therefore, electron affinity decreases. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger. This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period.

Noble Gases

noble gases are the group 8A elements on the far right of the table

Limiting Reagent

o You must have a balanced equation. o You must convert to moles first. o 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. o 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. https://www.khanacademy.org/science/chemistry/chemical-reactions-stoichiome/limiting-reagent-stoichiometry/v/limiting-reactant-example-problem-1

Third Quantum Number

o a.k.a. "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) The orientation of the orbital around the nucleus mℓ= -ℓ to +ℓ So if ℓ=0, then mℓ=0, means there is only one orientation around the nucleus, and a sphere only has one orientation around the nucleus ℓ=1, mℓ= -1, 0, +1, 3 possible values, this tells us that there are 3 possible orientations. We have 3 possible orientations for the p orbital, or the dumbbell shape.

Heat of Combustion

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. LESS STABLE BONDS=LOW ENERGY BONDS=HIGH ENERGY MOLECULE=HIGHER HEAT OF COMBUSTION 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 RELEASE 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 BONDS RELEASE ENERGY

Thermodynamics

the thermodynamics of a reaction reflect the potential reactivity (for example, given infinite reaction time) and includes all measurements of energy flow and relative stability. ∆H ∆G ∆S Keq 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). It is IMPERATIVE that students understand that the rate of a reaction is independent of its thermodynamic properties.

KE = E - φ

where E is the amount of energy added or photon energy KE is the kinetic energy of the ejected electron The amount of energy required to do this is called the "work function," and is usually given the variable φ, or the work function of the metal E can be replaced with hf, the formula for energy of a proton One of the most important take-home messages is that more INTENSE light [i.e., same wavelength, but more photons striking the metal per second] does NOT increase the KE of ejected photons, but DOES increase the number of photons ejected. Meanwhile, changing to a higher frequency light [i.e., blue light replacing red light] DOES increase the KE of the ejected electrons [as long as the work function has been exceeded].) Light intensity or wavelength does not increase KE, only increases # photos ejected Higher frequency DOES affect speed or KE of photons being ejected ex- 700J at a rate vs 1 X 10^5 protons vs 350J and a rate of photos at twice the first rate, means that the second source will eject twice as many electrons as the first. The left energy will be KE, which can be used to solve for velocity using 1/2mv^2=KE