Knowledge Organiser: Radioactive Decay
Part of Radioactive Decay · GCSE GCSE Physics revision
This topic summary covers Knowledge Organiser: Radioactive Decay within Radioactive Decay for GCSE Physics. Revise Radioactive Decay in Atomic Structure for GCSE Physics with 13 exam-style questions and 6 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 14 of 14 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 14 of 14
Practice
13 questions
Recall
6 flashcards
Knowledge Organiser: Radioactive Decay
Key Terms
- Alpha (α): 2p + 2n, charge +2
- Beta (β): Electron, charge −1
- Gamma (γ): EM wave, no charge
- Ionisation: Removing electrons from atoms
Key Facts
- Alpha: stopped by paper; most ionising
- Beta: stopped by aluminium
- Gamma: reduced by thick lead
- High ionising = low penetrating
- Decay is random and spontaneous
Nuclear Equation Changes
- Alpha: A − 4, Z − 2
- Beta: A same, Z + 1
- Gamma: A same, Z same
- Alpha + beta → element changes
Exam Tips
- Balance both A and Z in equations
- Alpha particle = ⁴₂He
- Beta particle = ⁰₋₁e
- Gamma = most penetrating, least ionising
Key Equations
- Alpha decay: A decreases by 4, Z decreases by 2
- Beta decay: A unchanged, Z increases by 1
- Gamma decay: A and Z both unchanged (energy released only)
- Activity (Bq) = number of decays per second
Common Mistakes
- Not balancing nuclear equations: Both the mass numbers (top) and atomic numbers (bottom) must balance on each side of the equation — always check both separately
- Confusing ionising power and penetrating power: Alpha is most ionising but least penetrating; gamma is least ionising but most penetrating — these properties are inversely related
- Saying gamma radiation changes the nucleus: Gamma emission releases energy but does not change the proton or neutron numbers — A and Z are both unchanged after gamma emission
- Confusing beta decay with electron emission from shells: Beta particles are emitted from the nucleus (a neutron converts to a proton + electron) — not from electron shells
- Forgetting that radioactive decay is random: Radioactive decay is spontaneous and random — it cannot be triggered or prevented by chemical reactions, temperature, or pressure
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Practice Questions for Radioactive Decay
An alpha particle consists of which particles?
Explain why alpha radiation is described as highly ionising but weakly penetrating.
Quick Recall Flashcards
13 questions on Radioactive Decay — practise free
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