Periodic trends and bonding appear in every IB Chemistry exam. For VSEPR, count all electron pairs (bonding + lone pairs) to determine geometry — lone pairs compress bond angles by approximately 2.5° each.

• Atomic structure: subatomic particles, electron configuration
• The Periodic Table: periodic trends (atomic radius, ionisation energy, electronegativity)
• Chemical bonding: ionic, covalent, metallic
• Intermolecular forces: van der Waals, dipole-dipole, hydrogen bonding
• VSEPR theory and molecular geometry
• Hybridisation (sp, sp², sp³)

Hess's Law questions require correctly reversing and scaling equations — sign errors are the most common mistake. Gibbs energy ΔG predicts spontaneity: negative ΔG means spontaneous. This combines enthalpy and entropy in one elegant calculation.

• Enthalpy changes: standard enthalpy of combustion, formation, neutralisation
• Hess's Law and enthalpy cycles
• Bond enthalpy calculations
• Born-Haber cycles (HL)
• Activation energy and Arrhenius equation
• Rate equations and reaction mechanisms (HL)
• Entropy, Gibbs energy: ΔG = ΔH − TΔS

For Kc expressions, products over reactants with correct stoichiometric powers. pH calculations for weak acids require the approximation [A⁻] ≈ [H⁺] — valid when Ka is small. Electrochemistry questions always require knowing which species is oxidised (loses electrons) and which is reduced.

• Dynamic equilibrium and Le Chatelier's principle
• Equilibrium constant Kc expressions
• Acid-base equilibria: Brønsted-Lowry theory, conjugate pairs
• pH calculations: strong and weak acids, Kw, Ka
• Buffer solutions: preparation and pH calculation
• Solubility product Ksp (HL)
• Electrochemistry: standard electrode potentials, electrolytic vs galvanic cells

IB Chemistry organic questions frequently ask for the mechanism or conditions, not just the product. For nucleophilic substitution, state the nucleophile, the bond broken, and the leaving group. NMR splitting follows the n+1 rule — n adjacent H atoms give n+1 peaks.

• Functional groups: alkanes, alkenes, alkynes, halogenoalkanes, alcohols, aldehydes, ketones, carboxylic acids, esters, amines
• Reaction types: substitution (free radical, nucleophilic), addition, elimination, condensation, hydrolysis
• Stereoisomerism: geometric (cis/trans) and optical (enantiomers, chiral centres)
• Spectroscopy: IR (key wavenumbers), ¹H NMR (chemical shifts, integration, splitting)
• Synthetic pathways (HL): multi-step organic synthesis