Chemistry

Chemical bonding

Ionic, covalent, and metallic bonds, plus molecular shape.

Basics

Ionic bond

Electrons transfer to make cations and anions; electrostatic attraction builds a lattice. Common for metal + nonmetal. High melting points; conducts when molten or dissolved.

Covalent bond

Atoms share electron pairs. A large electronegativity gap makes the bond polar. Bond counts usually complete an octet (or two electrons for hydrogen).

VSEPR

Electron domains repel and set shape. 2 domains: linear; 3: trigonal planar; 4: tetrahedral. Lone pairs repel more than bonding pairs and shrink angles.

Intermolecular forces

From weaker to stronger: London dispersion < dipole–dipole < hydrogen bonding (H on N, O, or F). These set boiling point, solubility, and viscosity.

Formulas

Formal charge

FC = V − N − B/2

Checks electron bookkeeping in a Lewis structure. Smaller absolute formal charges are usually better.

Symbols

V valence electrons
N nonbonding electrons
B bonding electrons

Ionic lattice force (qualitative)

F ∝ |q₁ q₂| / r²

Larger charges and smaller ionic radii raise lattice energy.

Symbols

q ionic charge
r internuclear distance

In this field

Atoms and the periodic table

Atomic structure, nucleus and electrons, periods and groups.

The mole and stoichiometry

Moles, molar mass, empirical formulas, and yield.

Gases and acids–bases

Ideal gas, pH, and buffers.

Thermo, equilibrium, kinetics

Enthalpy, Gibbs energy, K, and rate laws.

Electrochemistry and organic basics

Oxidation numbers, cells, Nernst, functional groups.

Nuclear chemistry

Radioactivity, half-life, binding energy.

Solutions and kinetics

Concentration, colligative properties, rate laws.

Analytical chemistry

Titration, spectroscopy, and chromatography — measuring what is present and how much.

Polymers and solids

Crystals and glasses, metal–ionic–covalent solids, polymer chains and the glass transition.

Coordination compounds

Ligands, coordination number, crystal field, colour, and an 18-electron sketch.

Electrochemical cells

Galvanic versus electrolytic, Nernst, Faraday, and a corrosion sketch.

Phase equilibria and diagrams

Gibbs phase rule, unary diagrams, eutectics, and the lever rule.