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Unit 2: Molecular and Ionic Compound Structure and Properties

7 dot points across 7 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does a potential-energy curve describe a covalent bond, and what controls bond length and bond energy?

Topic 2.2 Intramolecular Force and Potential Energy: interpret a potential-energy versus internuclear-distance curve to define bond length and bond energy, and explain how bond order, atomic size and charge affect bond strength.
A focused answer to AP Chemistry Topic 2.2, covering the potential-energy versus internuclear-distance curve, equilibrium bond length, bond energy, and how bond order, atomic radius and ionic charge control bond strength, with full worked reasoning.
10 min answer →

How do we draw a Lewis diagram that correctly shows the bonding and lone pairs in a molecule or ion?

Topic 2.5 Lewis Diagrams: draw Lewis diagrams for molecules and polyatomic ions, applying the octet rule and accounting for valence electrons, multiple bonds, and common exceptions.
A focused answer to AP Chemistry Topic 2.5, covering counting valence electrons, the octet rule, single and multiple bonds, lone pairs, polyatomic ions, and common octet exceptions, with a full worked drawing procedure.
10 min answer →

When several Lewis diagrams are possible, how do resonance and formal charge tell us the real structure?

Topic 2.6 Resonance and Formal Charge: draw resonance structures and use formal charge to select the most reasonable Lewis diagram, and explain how resonance describes delocalised bonding.
A focused answer to AP Chemistry Topic 2.6, covering resonance structures, the resonance hybrid, calculating formal charge, and using formal charge to choose the best Lewis diagram, with full worked examples.
10 min answer →

How does the lattice structure of an ionic solid explain its melting point, brittleness, and conductivity?

Topic 2.3 Structure of Ionic Solids: describe the lattice of an ionic solid, relate lattice energy to ionic charge and size using Coulomb's law, and explain the properties of ionic compounds from their structure.
A focused answer to AP Chemistry Topic 2.3, covering the ionic lattice, lattice energy, the Coulombic dependence on charge and ionic radius, and how the lattice explains high melting points, brittleness and conductivity only when molten or dissolved, with worked reasoning.
10 min answer →

How does the electron-sea model explain the properties of metals, and how do alloys modify them?

Topic 2.4 Structure of Metals and Alloys: use the electron-sea model to explain metallic properties, and describe how interstitial and substitutional alloys change those properties.
A focused answer to AP Chemistry Topic 2.4, covering the electron-sea model of metallic bonding, why metals conduct, are malleable and lustrous, and how interstitial and substitutional alloys alter properties, with worked reasoning.
9 min answer →

What determines whether a bond is ionic, covalent, or metallic, and how does electronegativity decide bond polarity?

Topic 2.1 Types of Chemical Bonds: classify bonds as ionic, covalent (polar or nonpolar), or metallic using electronegativity and the elements involved, and relate bond type to properties.
A focused answer to AP Chemistry Topic 2.1, covering ionic, covalent and metallic bonding, electronegativity difference, bond polarity, and how bond type explains the macroscopic properties of a substance, with full worked examples.
10 min answer →

How does VSEPR predict the shape of a molecule, and how does that shape relate to hybridization and polarity?

Topic 2.7 VSEPR and Bond Hybridization: use VSEPR theory to predict molecular geometry and bond angles, assign the hybridization of the central atom, and relate geometry to molecular polarity.
A focused answer to AP Chemistry Topic 2.7, covering VSEPR theory, electron-domain geometry, molecular shapes and bond angles, the effect of lone pairs, hybridization of the central atom, and how shape determines molecular polarity, with full worked examples.
11 min answer →