A one-page visual summary of Molecular & Ionic Compound Structure & Properties — every key topic, term, and theme you need to know for the exam, on a single screen.
Ionic / covalent / metallic bond — the three bonding types, distinguished by electronegativity difference and electron behavior.
Lattice energy — energy released forming an ionic solid; scales with charge and inversely with ionic radius.
Electron sea model — delocalized valence electrons in metals explain conductivity and malleability.
Octet rule — main-group atoms favor 8 valence electrons in Lewis structures.
Formal charge — bookkeeping tool used to evaluate which Lewis structure best represents a molecule.
Resonance structure — multiple valid Lewis structures differing only in electron placement; the real molecule is a hybrid.
VSEPR theory — electron domains (bonding + lone pairs) repel to minimize repulsion, determining shape.
Electron-domain vs. molecular geometry — they differ whenever lone pairs are present.
Hybridization (sp, sp², sp³) — orbital mixing that matches VSEPR-predicted geometry.
Sigma (σ) vs. pi (π) bonds — head-on overlap vs. side-by-side overlap; every multiple bond has exactly one sigma bond.
Key themes to remember
Electronegativity difference is your first move. Before anything else, estimate it to predict ionic vs. covalent vs. metallic bonding.
A Lewis structure is a model, not a snapshot of reality. Resonance and formal charge exist because real electron distributions are often a blend of multiple structures.
Lone pairs change everything about shape. Always count lone pairs before assuming a molecule's shape matches its electron-domain geometry.
Hybridization is the orbital story behind VSEPR. Don't think of them as two separate topics — VSEPR predicts the shape, hybridization explains why the orbitals support that shape.
This unit sets up Unit 3. Molecular shape and polarity determined here become the basis for intermolecular forces in the next unit.
Common exam traps
Don't confuse formal charge with actual ionic charge. Formal charge is a bookkeeping tool for comparing Lewis structures, not a real measured charge.
Resonance structures are not different molecules. They're different ways of drawing electron placement in the same single, real structure (the hybrid).
Electron-domain geometry ≠ molecular geometry whenever lone pairs exist. Don't report "tetrahedral" for water — water's molecular geometry is bent, even though its electron-domain geometry is tetrahedral.
A double bond does NOT mean two sigma bonds. Every double bond is exactly 1 sigma + 1 pi bond, not 2 sigma bonds.
Lattice energy trends follow charge first, then size. A doubly charged small ion (like O²⁻) typically dominates the lattice energy trend more than radius differences alone.