Chem Exam Review Flashcards
What is the Octet Rule?
A full valence = 8e- (except helium-only2). Elements gain/lose e- to achieve an octet, becoming ions.
What are Cations/Anions?
Cation=positive ion
Anion=negative ion
What is Ionization Energy
The quantity of energy required to remove an electron from an atom or ion in gaseous state.
How do you write an I.E. equation?
Lewis Symbol + I.E. -> [Cation]_++_e-
Ex. Li• + I.E. -> [Li]1+ + 1e-
What is Electron Affinity?
The quantity of energy change when an electron is added to the valence shell of an atom in gaseous state.
How do you write an E.A. equation?
Lewis Symbol + #e- -> [Anion]_- + E.A.
Ex. S•(x6) + 2e- -> [S•(x8)]2- + E.A.
What does Isoelectronic mean?
“Same electron configuration as”
What are Isotopes?
Atoms of an element with same # p+ and e- but differ in #no
What is Average Atomic Mass? What are the unit?
Average of the masses of all the isotopes of an element. Units are “u” (atomic mass units)
How do you calculate AverageAtomicMass?
AAM= mass(%abundance)+mass(%abundance)
Half Life & Equation
Time taken for half original #atoms to decay.
M<sub>r</sub>=M<sub>o</sub>x(½)<sup>#of half lives</sup> #half lives = total time / t (½)
What are the two factors that affect attraction for valence e-
Number of Orbits
Nuclear Charge
of Orbits
Row#(period)=#of Orbits
Electrostatic attraction between valence e- and the nucleus decrease as # of orbits increase (e- are farther away from protons)
Nuclear Charge
NC=# of protons in nucleus
Increases to the right of a period
Larger #= stronger electrostatic attraction
Ionic Radius Trend
Cations are smaller than their neutral atom
Anions are larger than their neutral atom
Multiple Ionization Energies Trend
First I.E.- energy to remove first e- (weakest hold)
Second I.E.- energy to remove second e- (more than 1st I.E.-protons pulling on less e-)
Third I.E. energy to remove third e- (more than first two-protons pull on less e-)
What is Metallic Character?
The ability to lose e-. Lower I.E. = more metallic
Non-Metallic Character
Higher E.A. = more reactive non-metal (ability to attract e-)
Electronegativity
EN is a measure of how well an atom can attract a shared pair of e- around it’s nucleus.
Trends in the Periodic Table
Down a group : Atomic radius and ionic radius increases, Metallic Character increases,
Across a period : Ionization Energy increases, Electron Affinity increases, Non-Metallic Character increases, Electronegativity (EN) increases
Expanded Octet
Elements in third row [and down] can be surrounded by more than 8 e- in order to minimize formal charge.
Guide to Balancing
- Metals
- Polyatomic ion groups
- Non-metals
- Hydrogen and oxygen
Sig Figs & Zeros
- Leading zeros don’t count
- Captive zeros always count
- Trailing zeros count
If x and / take least # of sig figs
If + and - take least # of decimal places
Law of Constant Composition
Any given compound has the same composition anywhere.
Adding or removing atoms changes compound into completely different substance.
H2O is always 88.9% O and 11.1% H
Percent Composition
% by mass of each element in a compound. (always the same no matter how large the sample)
%C = mass[Element] / total mass [Compound] x 100
Dissociation Equation
Shows soluble ionic compound breaking into ions in solution.
Ex. NaCl(s) -> Na+(aq) + Cl-(aq)
Dissolving Molecular Compounds
Most dissolve as molecules (except acids). Int.molec.forces are broken, bonds aren’t.
Therefore most molec.substances (except acids) are non-electrolytes [no mobile ions].
Solvents / Solubility Rules
Rule: Like dissolves like.
Polar solvents dissolve polar molecules due to DD forces
Non-polar solvents dissolve non-polar molecules due to LDF
*H2O - polar, C8H18 (gasoline) - non-polar*
Percent Concentration
v/v *units must be the same (5ml/100ml)
m/v *units are g/ml (4% = 4g/100ml)
m/m *units must be the same (2g/100g)
Low Concentrations
Parts per mil. - ppm: cppm= m/m x106
Parts per bil. - ppb: cppb= m/m x109
Parts per tril. - ppt: cppt= m/m x1012
pH
Power of Hydrogen - indicates amount of H3O+ in a solution
One unit of pH change means 10x change in H3O+ concentration
Ex. pH of 5 is 10x more acidic than pH of 6
How to calculate [H3O+] / pH
[H3O+] = 10-pH
If [H3O+] is _#x10-_mol/L = -log#_x10-_
Ex. 2.3x10-2mol/L -> -log2.3x10-2 = 1.6pH
*square brackets mean concentration*
pOH
pOH=7
[OH1-] = 10-7mol/L

Absolute Scale of Temperature
Celcius Kelvin
100oC 373K
0oC 273K
-273oC 0 K
Dalton’s Law of Partial Pressure
Ptotal = P1 + P2 + P3 …
*Collecting gas over water includes water vapour, therefore the partial pressure of water must be subtracted.
SATP and STP Values
SATP__STP
T : 25oC = 298K 0oC = 273k
P : 100kPa 101.3kPa
n : 1 mol 1 mol
V : 24.8L 22.4L
Percent Ionization
%ionization (p) = [H3O+] / [Acid] x100