OAT General Chemistry Review

Ionic Bonds:

-Electrons leave one atom (cation) and are held by another (anion).

Covalent Bonds:

-Electrons are shared between atoms.

-Sharing can be equal (pure covalent) or unequal (polar covalent).

Metallic Bonds:

-Delocalized electrons spread over the surface of a metal.

-D Orbital.

Lewis-Dot Structures:

-Dot is a free e- in a shell.

-Line is an e- pair in a bond.

Octet Rule:

-Most atoms form bonds to achieve 8 valence e-.

-Exceptions: Hydrogen, Lithium, Beryllium, Boron.

-Expanded Octet: Phosphorus, Sulfur, Chlorine. (Group 3 or higher).

Formal Charge:

*Formal charge = valence e- minus number of pi and sigma bonds attached minus nonbonding electrons.

*# Valence e- minus (sticks + dots).

Valence Electrons:

-The electrons in the outer shell that bond or react.

Resonance Structures:

-In molecules with open p orbitals, electrons can be delocalized or shared among atoms in more than one way, creating extra stabilization.

VSEPR:

-The shape of a molecule is determined among valence e-.

Pairs:

-Bonding pairs are less repulsive due to distribution of negative charge.

-NonBonding pairs are more repulsive due to localization of negative charge.

Electronic Geometry:

-Treats bonding and nonbonding the same; does not account for angle difference.

Molecular Geometry:

-Takes into account angle differences.

Intermolecular Forces (in decreasing strength).

*Forces between different molecules.

1.) Ion-Dipole.

2.) Hydrogen Bonding.

3.) Dipole-Dipole.

4.) Dipole-Induced Dipole (Debye).

5.) London Forces / Dispersion Forces.

Principal Quantum Number: (n)

-Higher n = higher energy level = larger radius.

Angular Quantum Number: (l)

-Value can be any integer from 0 to (n-1).

*0=s, 1=p, 2=d, 3=f.

Magnetic Quantum Number: (m)

-From -L to +L.

Spin Quantum Number: (Ms)

-Can either be -1/2 or +1/2.

Hund's Rule:

-Electrons fill into a subshell such that there a maximum number of half-filled, parallel spin orbitals.

Aufbau Principle:

-Electrons fill according to the (N+L) rule such that the subshell that has the smallest sum with the smallest n fills first.

Atomic Mass: (superscript)

-(Protons + Neutrons).

Atomic Number: (subscript)

-(# of protons).

Alkali Metals:

-Group 1.

-Form +1 cations.

-Highly reactive.

Alkaline Earth Metals:

-Group 2.

-Form +2 cations.

-Somewhat reactive.

Carbon Family:

-Group 4.

-Not easily ionizable.

Nitrogen Family:

-Group 5.

-Not easily ionizable.

Oxygen Family:

-Group 6.

-Form -2 anions.

-Somewhat reactive.

Halogens:

-Group 7.

-Form -1 anions.

-Highly reactive.

Noble Gases:

-Group 8.

-Do not form ions or react.

Metals:

-Groups 1 and 2.

-Form cations.

-Ductile, malleable, shiny, conductive.

Transition Metals:

-D block.

-May be able to form cations.

-Particularly hard metals with high melting and boiling points.

Nonmetals:

-Groups 6, 7, 8.

-Brittle, poor conductors.

Metalloids/Semimetals:

-Lower left p block. (staircase).

-Mixed properties, so specific characteristics are rarely tested.

Effective Nuclear Charge: (Zeff)

-The net positive charge a valence electron feels from the nucleus.

-Increases right and up.

Atomic Radius:

-Size of the atom.

-Decreases right and up.

Electronegativity:

-Degree of attraction an atom has for electrons in a chemical bond.

-Increases right and up.

Ionization Energy:

-Energy required to completely remove an electron from an atom.

-Increases right and up.

Electron Affinity:

-Energy released when an electron is added to an atom.

-Increases right and up.

Molecules:

-Two or more atoms held together.

-Ex.) H2

Compounds:

-Require those elements to be different.

-Ex.) H2O

Molecular Mass:

-The weight of one molecule in daltons.

Molar Mass:

-The weight of one mole of molecules in grams.

Mole:

=6*10^23

Empirical Formula:

-Uses the smallest whole number ratios of atoms.

-Ex.) CH2O

Molecular Formula:

-Use the actual number of atoms.

-Ex.) C6H12O6

Percent Composition:

-Percentage of mass contributed by each element in a compound.

-Mass of (x) in formula divided by formula weight of compound.

Limiting Reactant:

-The reactant completely consumed first, halting the forward reaction.

Theoretical yield:

-Maximum yield calculated.

-We never get this through experimentation.

Actual Yield:

-The experimental yield actually measured.

Percent Yield:

-(Actual Yield divided by Theoretical Yield) * 100.

Exothermic Reaction:

-Heat given off. (exiting the system).

- (-deltaH).

Enthalpy:

-The heat of a reaction.

-The total heat content (energy) of a system.

Endothermic Reaction:

-Heat is entering system.

-(+deltaH).

Radiation:

-Transfer of heat by electromagnetic waves.

-Ex.) Sunlight, Microwave.

Conduction:

-Transfer of heat through direct contact.

Convection:

-Transfer of heat through bulk motion.

Hess's Law:

-If a reaction can be broken down into a series of steps, the enthalpy change for the overall net reaction is the sum of the enthalpies of each step.

Entropy:

-The disorder of a system.

-The energy o a system unable to do work.

Gibbs Free Energy:

-The energy of a system able to do work.

Negative Delta G:

-A spontaneous reaction.

-Will proceed forward to make products.

Delta G = 0:

-A reaction at equilibrium.

-Will maintain the same concentrations.

Positive Delta G:

-A nonspontaneous reaction.

-Will proceed in reverse to make reactants.

Q

-Not yet reached equilibrium; rxn proceeds forward.

Q=Keq:

-At equilibrium; rate forward is equal to rate reverse.

Q>Keq:

-Overshot equilibrium; rxn proceeds in reverse.

LeChatelier's Principle:

-If a stress is applied to a system at equilibrium, the system will shift in such a way as to relieve the applied stress.

Qsp < Ksp:

-Unsaturated.

Qsp = Ksp:

-Saturated.

Qsp > Ksp:

-Supersaturated.

Molar Solubility:

-Concentration at saturation.

Reaction Concentration:

-Increasing [M] generally increases rate, up to a maximum.

Temperature:

-Increasing T generally increases rate, up to a maximum.

Medium:

-Some reactions perform better in certain media.

-Ex.) Polar vs. Nonpolar.

Catalyst:

-Catalysts (such as enzymes) increase rate by decreasing activation energy.