Edexcel GCSE Physics
Edexcel GCSE Physics Topic 6: Radioactivity Exam Questions
Free Edexcel GCSE Physics exam questions for Topic 6: Radioactivity, with a mark scheme for every pack. Covers atomic structure, isotopes, alpha, beta, gamma and neutron radiation, nuclear equations, half-life, uses, dangers, fission and fusion.
Topic 6: Radioactivity exam questions
3 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel GCSE Physics Topic 6: Radioactivity
Topic 6 on Paper 1 covers the structure of the atom, how models of the atom developed, and why some nuclei are unstable. You need to describe alpha, beta minus, beta plus, gamma and neutron emissions, balance nuclear equations and use half-life, including from graphs. The topic also covers background radiation, the difference between irradiation and contamination, medical uses such as tracers and radiotherapy, and, in separate physics, nuclear fission in reactors and nuclear fusion in stars. Examiners regularly test half-life calculations, penetrating power and ionising ability, and how the plum pudding model was replaced after the alpha particle scattering experiment.
What you need to know
- Atomic structure An atom has a tiny positive nucleus of protons and neutrons with electrons in shells. Isotopes have the same number of protons but different numbers of neutrons. Electrons move between shells when they absorb or emit electromagnetic radiation.
- Models of the atom Thomson's plum pudding model was replaced after Rutherford's alpha particle scattering experiment showed most of the atom is empty space with a small, dense, positive nucleus. Bohr added electrons in fixed energy levels.
- Types of radiation Alpha: 2 protons and 2 neutrons, highly ionising, stopped by paper. Beta minus: fast electron, stopped by a few mm of aluminium. Gamma: EM wave, weakly ionising, reduced by thick lead. Beta plus is a positron.
- Nuclear equations Alpha decay reduces mass number by 4 and atomic number by 2. Beta minus decay leaves mass number unchanged and increases atomic number by 1 as a neutron turns into a proton.
- Half-life The time for half the undecayed nuclei, or the activity, to halve. Activity is measured in becquerels (Bq) using a Geiger-Muller tube.
- Uses and hazards Tracers, radiotherapy, smoke alarms, sterilising equipment. Irradiation is exposure from outside; contamination is when radioactive material gets onto or into an object.
- Fission and fusion Fission: a neutron is absorbed by uranium-235, which splits into two daughter nuclei and releases 2 or 3 neutrons and energy, allowing a chain reaction controlled by control rods and a moderator. Fusion joins light nuclei and powers stars, but needs very high temperature and pressure.
Common mistakes in Topic 6: Radioactivity
- Saying gamma rays are the most ionising. Alpha is the most ionising; gamma is the most penetrating.
- Confusing irradiation with contamination, or saying irradiated objects become radioactive. Irradiated objects do not become radioactive.
- Changing the mass number in beta decay. In beta minus decay the mass number stays the same and the atomic number goes up by 1.
- Saying half-life is half the time for all the nuclei to decay. It is the time for the number of undecayed nuclei or the activity to halve.
- Mixing up fission and fusion. Fission splits a heavy nucleus; fusion joins light nuclei.
Try three Topic 6: Radioactivity exam-style questions
1. A sample's activity falls from 800 Bq to 100 Bq in 18 hours. Calculate its half-life. (3 marks)
Show the mark scheme answer
800 to 400 to 200 to 100 is 3 half-lives; 18 / 3; half-life = 6 hours.
2. Radium-226 (atomic number 88) decays by alpha emission into radon. State the mass number and atomic number of the radon nucleus. (2 marks)
Show the mark scheme answer
Mass number = 222; atomic number = 86.
3. Describe what happens in a nuclear fission chain reaction. (4 marks)
Show the mark scheme answer
A uranium-235 nucleus absorbs a neutron; it splits into two smaller daughter nuclei; releasing 2 or 3 neutrons and energy; these neutrons are absorbed by further uranium nuclei causing more fissions.
Topic 6: Radioactivity FAQs
What does Edexcel GCSE Physics Topic 6 Radioactivity cover?
It covers atomic structure and models of the atom, types of nuclear radiation, nuclear equations, half-life, uses and dangers of radiation, and fission and fusion.
Which paper is Topic 6 examined on?
Topic 6 is assessed on Paper 1.
How do I answer half-life questions?
Count how many times the activity or number of nuclei halves, then divide the total time by that number, or read the time for the value to halve from a decay graph.
