Radioactive decay and nuclear radiation

    AQA
    GCSE

    Radioactive decay is the random, stochastic process by which unstable atomic nuclei emit radiation to achieve a more stable nuclear configuration. This topic necessitates a detailed understanding of the properties, ionizing power, and penetrating capabilities of alpha particles, beta particles, and gamma rays, alongside the conservation laws governing nuclear equations. Candidates must also apply the mathematical concept of half-life to model decay rates and critically evaluate the distinct hazards posed by irradiation versus contamination in medical and industrial contexts.

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    Objectives
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    Exam Tips
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    Pitfalls
    5
    Key Terms
    4
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for correctly identifying that in alpha decay, the mass number decreases by 4 and the atomic number decreases by 2
    • Credit responses that define half-life as the time taken for the number of radioactive nuclei in an isotope to halve
    • Award 1 mark for stating that irradiation does not cause the object to become radioactive, whereas contamination involves the presence of radioactive atoms
    • In beta decay equations, award marks for showing the mass number remains unchanged while the atomic number increases by 1

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for correctly identifying that in alpha decay, the mass number decreases by 4 and the atomic number decreases by 2
    • Credit responses that define half-life as the time taken for the number of radioactive nuclei in an isotope to halve
    • Award 1 mark for stating that irradiation does not cause the object to become radioactive, whereas contamination involves the presence of radioactive atoms
    • In beta decay equations, award marks for showing the mass number remains unchanged while the atomic number increases by 1

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When calculating half-life from a graph, always deduct the background count rate first if the graph does not level off at zero
    • 💡For 6-mark questions on safety, structure your answer by source: identify the radiation type, its penetrating power, and the specific shielding or distance required
    • 💡Memorize that a beta particle is an electron emitted from the nucleus when a neutron turns into a proton; this explains the atomic number change

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing the definitions of irradiation and contamination, often stating that irradiated objects become radioactive
    • Defining half-life vaguely as 'the time for radiation to stop' or 'time for the substance to decay' without reference to halving activity or nuclei count
    • Failing to account for background radiation when calculating the count rate from a source in experimental data questions

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

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    Practical Links

    Related required practicals

    • •{"code":"Standard Demonstration","title":"Investigation of radiation penetration","relevance":"Using GM tube and absorbers (paper, aluminium, lead) to identify alpha, beta, gamma"}

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