Chemistry lessons
A level & IB Chemistry: atomic structure, bonding, energetics, equilibria, organic chemistry, and practical skills.
Key topics
- Atomic structure & periodicity
- Bonding & structure
- Energetics & kinetics
- Equilibria & acids
- Organic chemistry
- Practical & calculations
Lesson course
Work through each lesson, run the interactive practice, and tick it off as you go.
1. Atomic structure & periodicity
Core
Atomic structure & isotopes
Describe sub-atomic particles and isotopes.
Atoms have a nucleus of protons (+) and neutrons, with electrons (−) in shells. Atomic number = protons; mass number = protons + neutrons. Isotopes share protons but differ in neutrons.
Work out protons, neutrons and electrons for five isotopes.
Electron configuration
Write configurations using s, p, d subshells.
Electrons fill subshells by energy: 1s 2s 2p 3s 3p 4s 3d… Each orbital holds 2 electrons of opposite spin.
Write electron configurations for elements 1–20.
Periodic trends
Explain trends in ionisation energy and radius.
Across a period nuclear charge rises and radius falls, so ionisation energy generally increases. Down a group radius increases and ionisation energy falls.
Explain the trend in first ionisation energy across period 3.
2. Bonding & structure
Core
Ionic & covalent bonding
Compare electron transfer and sharing.
Ionic bonding transfers electrons forming ions held by electrostatic attraction; covalent bonding shares electron pairs between atoms.
Draw dot-and-cross diagrams for one ionic and one covalent compound.
Shapes of molecules
Predict shapes using electron-pair repulsion.
Electron pairs repel to minimise repulsion (VSEPR): 2 pairs linear 180°, 3 trigonal planar 120°, 4 tetrahedral 109.5°. Lone pairs repel more.
Predict and name shapes for four simple molecules.
Intermolecular forces
Relate forces to physical properties.
Between molecules: London (induced dipole), permanent dipole–dipole, and hydrogen bonding (involving N, O or F with H). Stronger forces → higher boiling points.
Rank three substances by boiling point and justify it.
3. Energetics & kinetics
Core
Enthalpy & Hess's law
Use enthalpy changes and energy cycles.
Exothermic reactions release heat (ΔH negative); endothermic absorb it (positive). Hess's law: the enthalpy change is independent of route.
Use Hess's law to find one enthalpy change.
Rates & collision theory
Explain factors affecting reaction rate.
Particles must collide with at least the activation energy and the right orientation. Higher concentration, temperature or surface area increases collision frequency or energy.
Explain how three factors change reaction rate.
Catalysts
Explain how catalysts work.
A catalyst provides an alternative route with lower activation energy and is not used up in the reaction.
Sketch an energy profile with and without a catalyst.
4. Equilibria & acids
Core
Equilibrium & Le Chatelier
Predict shifts in dynamic equilibria.
At equilibrium forward and reverse rates are equal. Le Chatelier: a system opposes a change — more pressure favours fewer gas moles; more heat favours the endothermic direction.
Predict the effect of pressure and temperature on one equilibrium.
Acids, bases & pH
Use the Brønsted model and pH.
Acids donate H⁺ (protons); bases accept them. pH = −log[H⁺], so a lower pH means a more acidic solution.
Calculate pH from hydrogen-ion concentration for two acids.
Titrations
Find unknown concentrations by titration.
A titration reacts an unknown against a standard solution to an indicator end point; moles = concentration × volume.
Complete one titration calculation from given data.
5. Organic chemistry
Core
Alkanes & alkenes
Distinguish saturated and unsaturated hydrocarbons.
Alkanes are saturated (single C–C bonds); alkenes contain a C=C double bond and undergo addition reactions.
Write equations for combustion and addition reactions.
Alcohols & halogenoalkanes
Identify functional groups and reactions.
Alcohols contain the –OH group and can be oxidised; halogenoalkanes contain a carbon–halogen bond and undergo nucleophilic substitution.
Classify alcohols and write one substitution reaction.
Reaction mechanisms
Use curly arrows to show mechanisms.
Mechanisms use curly arrows to show electron-pair movement — e.g. electrophilic addition to alkenes or nucleophilic substitution of halogenoalkanes.
Draw the mechanism for one addition or substitution.
6. Practical & calculations
Skills
Required practicals
Carry out and evaluate core techniques.
Master titration, making standard solutions, measuring rates, and recording precise observations with correct apparatus.
Write a method for making a standard solution.
Moles & yield
Use the mole concept in calculations.
Moles = mass ÷ Mr. Use balanced equations for reacting ratios; percentage yield = actual ÷ theoretical × 100.
Calculate reacting masses and a percentage yield.
Mock exam paper
Apply skills under timed conditions.
Practise calculations and mechanisms to time; show working for method marks and always include units.
Sit one past paper, then mark and correct it.
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