What is the difference between nuclear fission and fusion?
Fission splits a heavy nucleus into smaller ones; fusion joins light nuclei into a heavier one. Learn it step by step →
Nuclear & Particle Physics is a core part of A-Level Physics. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Atomic structureA tiny nucleus of protons and neutrons with electrons in shells.
Alpha, beta & gammaTypes of nuclear radiation with different penetration and ionising power.
Half-lifeTime for half the undecayed nuclei to decay.
Nuclear fissionSplitting a large nucleus, releasing energy.
Nuclear fusionJoining small nuclei, releasing energy (powers stars).
Fundamental particlesQuarks and leptons; protons and neutrons are made of quarks.
Mass defectΔm = (sum nucleon masses) − nuclear mass.
E = mc²Energy released equals lost mass × c².
Binding energyEnergy to separate nucleus into nucleons.
BE per nucleonBinding energy ÷ number of nucleons.
FissionLarge nucleus splits, releasing energy.
FusionSmall nuclei combine, releasing energy.
ActivityDecays per second, A = λN, measured in Bq.
Decay constantλ = probability of decay per second.
What your exam board covers
Where Nuclear & Particle Physics sits in each exam board's specification. Tap a board to see what it lists.
Questions where students often pick the tempting wrong answer — make sure you know the right one:
What is the difference between nuclear fission and fusion?✗ Fission and fusion are the same process, just at different scales.✓ Fission splits a heavy nucleus into smaller ones; fusion joins light nuclei into a heavier one.
In a balanced nuclear equation, what must be equal on both sides?✗ Only the atomic number (proton count) needs to balance.✓ The total mass number (top numbers) and the total atomic number (bottom numbers) must both balance.
Which type of nuclear radiation is most ionising?✗ Gamma is most ionising because it can travel furthest and pass through almost anything.✓ Alpha radiation — large, doubly charged particles cause the most ionisation per unit distance.
Is a radioactive sample completely gone after two half-lives?✗ Yes — two halves make the whole sample decay.✓ No — each half-life halves what remains, so one quarter is still undecayed after two half-lives.
Why did some alpha particles bounce back in Rutherford's experiment?✗ They collided with electrons spread throughout the atom.✓ They approached a tiny, dense, positively charged nucleus almost head-on and were repelled.
Practise Nuclear & Particle Physics — free games
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