AP Chemistry / Topic
Molecular and Ionic Compound Structure and Properties
Unit 2 covers the bonding models — ionic, covalent, and metallic — plus Lewis diagrams, resonance, formal charge, VSEPR geometry, and bond polarity. The exam tests whether you can predict structure and then connect structure to properties.
What the exam asks
- Classify bonds as ionic, polar covalent, or nonpolar covalent from electronegativity differences
- Draw Lewis structures, evaluate resonance forms, and use formal charge to pick the best structure
- Predict electron and molecular geometry, bond angles, and hybridization with VSEPR
- Determine whether a molecule is polar from its geometry and bond dipoles
- Explain properties of ionic solids, metals, and alloys with lattice and sea-of-electrons models
Key formulas and rules
FC = valence electrons − nonbonding electrons − ½(bonding electrons)
2 domains: linear 180°; 3: trigonal planar 120°; 4: tetrahedral 109.5°
4 domains with 1 lone pair: trigonal pyramidal; with 2: bent
higher bond order ⇒ shorter, stronger bond
polar bonds + asymmetric shape ⇒ polar molecule; symmetric shapes cancel dipoles
Question bank breakdown
34
1
8 easy · 16 medium · 10 hard
Skills covered
Every question in the bank comes with a per-choice explanation, so you learn why each wrong answer is wrong — not just the key.
Sample question
From the free tier of the ScoreMint AP Chemistry bank — try it, then check the answer.
Which of the following compounds is expected to have the highest melting point?
- A. NaCl (sodium chloride)
- B. CH₄ (methane)
- C. CO₂ (carbon dioxide)
- D. H₂O (water)
Show answer and explanation
Answer: A. Correct. NaCl is an ionic compound with a crystal lattice structure held together by strong electrostatic forces between Na⁺ and Cl⁻ ions. Breaking this lattice requires a large amount of energy. NaCl melts at 801°C. Ionic bonds are far stronger than the intermolecular forces in molecular compounds. ✓
Study tip
When two Lewis structures both obey the octet rule, compute formal charges: the best structure minimizes formal charge and puts any negative formal charge on the more electronegative atom.