CHEM 104 Pre Semester Review

Atom

Basic unit of matter, consisting of protons, neutrons, and electrons.

Ion

An atom or molecule with a net electric charge due to gain or loss of electrons.

Cation

Positively charged ion (loss of electrons).

Anion

Negatively charged ion (gain of electrons).

Atomic number

Number of protons in the nucleus of an atom.

Mass number

Sum of protons and neutrons.

Periodic trend

Predictable changes in element properties across the periodic table.

Electronegativity

Atom’s ability to attract electrons in a bond.

Ionic bond

Electrostatic attraction between oppositely charged ions.

Covalent bond

Bond formed by sharing electrons between atoms.

Polar covalent bond

Electrons shared unequally, creating partial charges.

Nonpolar bond

Electrons shared equally; no net charge.

VSEPR theory

Predicts molecular shape based on repulsion between electron pairs.

Linear molecule

180° bond angles (e.g., CO₂).

Bent molecule

Trigonal planar

120° angles, 3 bonding pairs (e.g., BF₃).

Tetrahedral

109.5° angles (e.g., CH₄).

Stoichiometry

Calculation of reactants/products in chemical reactions.

Limiting reactant

Substance that determines the maximum product formed.

Mole

6.022 × 10²³ particles.

Molar mass

Mass of 1 mole of a substance (g/mol).

Ideal Gas Law

PV = nRT

Enthalpy (ΔH)

Heat content of a system at constant pressure.

Endothermic

Absorbs heat (ΔH > 0).

Exothermic

Releases heat (ΔH < 0).

Heat capacity

Amount of heat needed to raise temperature of a substance.

Intermolecular forces

Forces between molecules: London, dipole-dipole, hydrogen bonding.

London dispersion

Weakest IMF; present in all molecules.

Hydrogen bond

Strong IMF involving H bonded to N, O, or F.

Equilibrium

Forward and reverse reactions occur at the same rate.

Le Châtelier’s Principle

A system at equilibrium shifts to minimize a disturbance.

K (equilibrium constant)

Describes the ratio of products to reactants at equilibrium.

Reaction rate

Change in concentration of a reactant or product over time.

Rate law

Expression relating rate to concentration of reactants.

Activation energy (Ea)

Minimum energy required to initiate a reaction.

Catalyst

Substance that speeds up reaction by lowering activation energy.

Redox reaction

Reaction involving transfer of electrons.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

Electrochemical cell

Device that converts chemical energy into electrical energy.

Anode

Site of oxidation in a redox reaction.

Cathode

Site of reduction in a redox reaction.

Nernst equation

Calculates cell potential under non-standard conditions.

Ammonium

NH₄⁺

Acetate

C₂H₃O₂⁻ or CH₃COO⁻

Carbonate

CO₃²⁻

Bicarbonate (Hydrogen carbonate)

HCO₃⁻

Hydroxide

OH⁻

Nitrate

NO₃⁻

Nitrite

NO₂⁻

Sulfate

SO₄²⁻

Sulfite

SO₃²⁻

Phosphate

PO₄³⁻

Hydrogen phosphate

HPO₄²⁻

Dihydrogen phosphate

H₂PO₄⁻

Chromate

CrO₄²⁻

Dichromate

Cr₂O₇²⁻

Permanganate

MnO₄⁻

Cyanide

CN⁻

Peroxide

O₂²⁻

Hypochlorite

ClO⁻

Chlorite

ClO₂⁻

Chlorate

ClO₃⁻

Perchlorate

ClO₄⁻

Tera

T 10¹²

Giga

G 10⁹

Mega

M 10⁶

Kilo

k 10³

Deci

d 10⁻¹

Centi

c 10⁻²

Milli

m 10⁻³

Micro

µ 10⁻⁶

Nano

n 10⁻⁹

Pico

p 10⁻¹²

Femto

f 10⁻¹⁵