IB Group 4 · Sciences
Chemistry
2025 syllabus · First assessment 2025
Structure and Reactivity, built on the guide’s understandings. Each note is tied to exactly what you must know — pitched to the command term the syllabus attaches to it, with SL and Additional HL content clearly split.
S1. Structure 1: Models of the particulate nature of matter
What matter is made of: elements, compounds and mixtures; the nuclear atom and isotopes; electron configurations and spectra; the mole and quantitative chemistry; and the ideal gas model.
S1.1 — Introduction to the particulate nature of matter
Elements, compounds and mixtures — Distinguishing the three, the separation techniques for mixtures, and homogeneous vs heterogeneous mixtures.
States of matter and temperature — The kinetic molecular theory, state symbols, changes of state, and temperature as average kinetic energy (Kelvin vs Celsius).
S1.2 — The nuclear atom
Atoms, isotopes and relative atomic mass — The nuclear symbol, sub-atomic particles, isotopes, and calculating relative atomic mass from isotopic abundance.
Mass spectra — Interpreting a mass spectrum for the identity and relative abundance of isotopes.
S1.3 — Electron configurations
Emission spectra and energy levels — The electromagnetic spectrum, continuous vs line spectra, the hydrogen emission spectrum, and discrete energy levels.
Orbitals and electron configuration — Sub-levels and orbital shapes, and writing electron configurations with the Aufbau principle, Hund’s rule and the Pauli exclusion principle.
Ionization energy — The convergence limit as ionization, trends in first ionization energy, and using ionization data.
S1.4 — Counting particles by mass: The mole
The mole and molar mass — The mole and the Avogadro constant, relative atomic and formula mass, and mass–mole–particle calculations.
Formulae and composition — Empirical vs molecular formula, and determining them from percentage composition and molar mass.
Concentration and gas volumes — Molar concentration, and using Avogadro’s law and mole ratios with gas volumes.
S1.5 — Ideal gases
The ideal gas model — The assumptions of the ideal gas model and why real gases deviate from it.
Gas laws and calculations — The ideal gas equation and combined gas law, and the pressure–volume–temperature relationships.
S2. Structure 2: Models of bonding and structure
How atoms bond: the ionic, covalent and metallic models; molecular shapes and intermolecular forces; the bonding continuum; and how bonding determines the properties of materials.
S2.1 — The ionic model
Forming ions and ionic bonds — How ions form, the ionic bond, and deducing the formulae and names of ionic compounds (including polyatomic ions).
Ionic lattices and properties — The 3D lattice, and explaining the physical properties of ionic compounds and lattice enthalpy.
S2.2 — The covalent model
Covalent bonds and Lewis formulas — Covalent and coordination bonds, the octet rule, Lewis formulas, and single/double/triple bonds.
Molecular shapes (VSEPR) and polarity — Predicting shapes with VSEPR, and deducing bond and molecular polarity.
Giant covalent structures and intermolecular forces — Covalent network solids, the intermolecular forces, and explaining physical properties (with chromatography).
Resonance, benzene and expanded octets — Resonance and delocalization, benzene, expanded octets, and formal charge.
Sigma and pi bonds, and hybridization — Sigma and pi bonds, and sp/sp²/sp³ hybridization.
S2.3 — The metallic model
Metallic bonding and properties — The metallic bond, and explaining the properties and melting-point trends of metals.
Transition metals — How delocalized d-electrons give transition elements high melting points and conductivity.
S2.4 — From models to materials
The bonding continuum — Bonding as a continuum, and the bonding triangle from electronegativity data.
Alloys and polymers — Alloys and non-directional bonding, and addition polymers.
Condensation polymers — Forming polyamides and polyesters by condensation.
S3. Structure 3: Classification of matter
Organizing the elements and organic compounds: the periodic table and periodicity, and the classification of organic molecules by functional group, with transition-metal chemistry and spectroscopy at HL.
S3.1 — The periodic table: Classification of elements
The periodic table and electron configuration — Periods, groups and blocks, and deducing electron configuration from an element’s position.
Periodic trends — Explaining the periodicity of atomic and ionic radius, ionization energy, electron affinity and electronegativity.
Group trends, oxides and oxidation states — Group 1 and 17 reactions, the acid–base character of oxides, and assigning oxidation states.
Transition elements — The characteristic properties of transition elements, their ion configurations, and coloured complexes.
S3.2 — Functional groups: Classification of organic compounds
Representing organic molecules — The types of organic formula and interconverting between them.
Functional groups and homologous series — The functional groups and homologous series, and trends in their physical properties.
IUPAC naming and isomers — Naming organic compounds and recognizing structural isomers.
Stereoisomerism — Cis–trans isomerism and optical isomerism around a chiral carbon.
Spectroscopy: MS, IR and NMR — Deducing structures from mass spectra, infrared spectra and ¹H NMR.
R1. Reactivity 1: What drives chemical reactions?
Energetics: measuring enthalpy changes, energy cycles (bond enthalpies, Hess’s law, Born–Haber), energy from fuels, and, at HL, entropy and Gibbs energy as the driver of spontaneous change.
R1.1 — Measuring enthalpy changes
Energy, enthalpy and energy profiles — Energy transfer, endothermic vs exothermic reactions, and reading energy profiles.
Calorimetry: calculating enthalpy change — Using Q = mcΔT and ΔH = −Q/n to find the enthalpy change of a reaction.
R1.2 — Energy cycles in reactions
Bond enthalpies — Calculating enthalpy changes from average bond enthalpies, and why they are averages.
Hess’s law — Using Hess’s law to find enthalpy changes in multistep reactions.
Formation, combustion data and Born–Haber cycles — Using ΔHf and ΔHc data, and interpreting Born–Haber cycles.
R1.3 — Energy from fuels
Combustion of fuels — Deducing equations for the complete and incomplete combustion of fuels.
Fossil fuels, biofuels and fuel cells — The pros and cons of fuels, renewable vs non-renewable sources, and fuel-cell half-equations.
R1.4 — Entropy and spontaneity
Entropy — Entropy as the dispersal of matter and energy, and calculating standard entropy changes.
Gibbs energy and spontaneity — Using ΔG = ΔH − TΔS to decide whether and when a reaction is spontaneous, and linking ΔG to K.
R2. Reactivity 2: How much, how fast and how far?
The amount, rate and extent of reactions: stoichiometry and yield; collision theory, rate laws and the Arrhenius equation; and dynamic equilibrium and Le Châtelier’s principle.
R2.1 — How much? The amount of chemical change
Chemical equations and reacting quantities — Balancing equations and using mole ratios to find reacting masses, volumes and concentrations.
Yield and atom economy — Limiting reactants, percentage yield, and atom economy.
R2.2 — How fast? The rate of chemical change
Rate and collision theory — Rate of reaction, and collision theory (energy and orientation).
Factors affecting rate; activation energy and catalysts — The factors that change rate, activation energy, Maxwell–Boltzmann curves, and catalysts.
Reaction mechanisms and rate equations — The rate-determining step, molecularity, and deducing rate equations and order.
The Arrhenius equation — The temperature dependence of the rate constant, and finding Ea from data.
R2.3 — How far? The extent of chemical change
Dynamic equilibrium and the equilibrium constant — Dynamic equilibrium and the equilibrium constant K.
Le Châtelier’s principle — Predicting the response of an equilibrium to changes in conditions.
Reaction quotient, K calculations and Gibbs energy — The reaction quotient Q, equilibrium calculations, and ΔG = −RT ln K.
R3. Reactivity 3: What are the mechanisms of chemical change?
The mechanisms of change: proton transfer (acids and bases), electron transfer (redox and electrochemistry), electron sharing (radicals), and electron-pair sharing (nucleophiles and electrophiles).
R3.1 — Proton transfer reactions
Brønsted–Lowry acids and bases — Proton donors and acceptors, conjugate acid–base pairs, and amphiprotic species.
pH, Kw and strong vs weak — The pH scale, the ionic product of water, and strong vs weak acids and bases.
Neutralization and pH curves — Neutralization reactions, the parent acid and base of a salt, and pH curves.
pOH, Ka, Kb and salt hydrolysis — The pOH scale, acid/base dissociation constants, and the pH of salt solutions.
pH curves, indicators and buffers — Reading the four types of pH curve, choosing indicators, and how buffers work.
R3.2 — Electron transfer reactions
Oxidation, reduction and half-equations — Oxidation states, oxidizing and reducing agents, half-equations, and reactivity.
Electrochemical cells — Voltaic (primary), secondary and electrolytic cells.
Organic redox — Oxidation and reduction of alcohols and carbonyls, and the hydrogenation of unsaturated compounds.
Electrode potentials and aqueous electrolysis — Standard electrode potentials, cell potential and spontaneity, and the electrolysis of solutions.
R3.3 — Electron sharing reactions
Radical reactions — Radicals and the initiation, propagation and termination of radical substitution in alkanes.
R3.4 — Electron-pair sharing reactions
Nucleophiles, electrophiles and heterolytic fission — Nucleophiles and electrophiles, heterolytic fission, and nucleophilic substitution.
Electrophilic addition to alkenes — The reactions of alkenes with water, halogens and hydrogen halides.
Lewis acids and bases, complexes and SN1/SN2 — Lewis acid–base theory, complex ions, and the SN1 and SN2 mechanisms.
Electrophilic addition and substitution mechanisms — Addition mechanisms and Markovnikov’s rule, and electrophilic substitution of benzene.
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