7(b) Radioactivity
Pearson Edexcel International GCSE Physics · 4PH1
Paper 1 | Whole paper: Core content, all eight topics
Unstable nuclei, the three emissions, and the half-life that makes decay predictable in bulk and random in detail.
Specification coverage
Topic 7 Radioactivity and particles (b) Radioactivity — statements 7.4–7.15
Assessment objectives: AO1, AO2. Suggested learning time: 70 minutes.
Required knowledge
- The structure of the atom and the meaning of atomic number, mass number and isotope
- The nature of alpha, beta and gamma radiation, their penetrating power and ionising ability
- Nuclear equations for alpha and beta decay
- Background radiation and its sources
- Half-life, and how to determine it from a graph or a table of data
- The dangers of ionising radiation and how exposure is reduced
Required skills
- Balance a nuclear equation for mass number and atomic number
- Determine half-life from decay data
- Select a suitable isotope for a use, and justify it by half-life and radiation type
How it is examined
- Multiple-choice and short-answer recall
- Calculations using the specification's relationships
- Extended open-response applying the physics to an unfamiliar situation
Common mistakes
- Treating decay as predictable for a single nucleus. Decay is random; half-life is a statistical property of a large sample.
- Forgetting that background radiation must be subtracted from a count rate before calculating half-life.
- Mixing up penetration and ionisation: alpha is the most ionising and the least penetrating.