GCSE Physics (AQA) chapter 4: Atomic structure MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

34 exam-style questions on Atomic structure, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

34 questions · 3 topics · 10 per test

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What chapter 4 covers

Ten Atomic structure questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. What is a chain reaction in nuclear fission?

  1. A
    two light nuclei joining one after another
  2. B
    nuclei decaying randomly one after another
  3. C
    neutrons released by fission go on to cause more fission events
  4. D
    alpha particles released by fission cause fusion
Show answer

Answer: C. Each fission releases two or three neutrons. If these are absorbed by other U-235 nuclei, they split too, and the process repeats.

2. Where does the energy released in nuclear fusion come from?

  1. A
    some of the mass of the nuclei is converted into energy
  2. B
    chemical bonds between atoms break
  3. C
    electrons move down to lower energy levels
  4. D
    neutrons are absorbed by the nuclei
Show answer

Answer: A. The mass of the heavier nucleus is slightly less than the total mass of the nuclei that joined. This missing mass is converted into energy.

3. Which is a natural source of background radiation?

  1. A
    fallout from nuclear weapons testing
  2. B
    medical X-rays
  3. C
    radon gas from rocks
  4. D
    nuclear accidents
Show answer

Answer: C. Rocks and cosmic rays are natural sources. Weapons testing, nuclear accidents and medical uses are man-made sources.

4. What is nuclear fusion?

  1. A
    splitting a large nucleus into two smaller nuclei
  2. B
    a nucleus emitting an alpha particle
  3. C
    a heavy nucleus absorbing a neutron
  4. D
    two light nuclei joining to form a heavier nucleus
Show answer

Answer: D. Fusion joins light nuclei such as hydrogen to make heavier ones such as helium. Splitting a heavy nucleus is fission.

5. What must happen to a uranium-235 nucleus before it undergoes fission in a reactor?

  1. A
    it must absorb a neutron
  2. B
    it must absorb a proton
  3. C
    it must emit an alpha particle
  4. D
    it must join with another nucleus
Show answer

Answer: A. Induced fission starts when a U-235 nucleus absorbs a neutron, making it unstable so it splits.

6. In what unit is radiation dose measured?

  1. A
    sieverts
  2. B
    counts per minute
  3. C
    becquerels
  4. D
    hertz
Show answer

Answer: A. Radiation dose, a measure of the risk of harm, is measured in sieverts (Sv). Activity is measured in becquerels.

7. Gamma rays from a source outside the body are used to treat a tumour. Why are the beams aimed at the tumour from several different directions?

  1. A
    to make the gamma rays more ionising
  2. B
    to shorten the half-life of the source
  3. C
    to make the tumour radioactive
  4. D
    so the tumour receives a high dose while the healthy tissue around it receives a lower dose
Show answer

Answer: D. All the beams overlap at the tumour, which gets a large dose to destroy the cells, while each path through healthy tissue gets only part of the dose.

8. Sources X and Y start with the same activity. X has a half-life of 2 days and Y has a half-life of 500 years. Which statement is correct?

  1. A
    the activity of X falls quickly, so it is a hazard for a short time; Y stays hazardous for a very long time
  2. B
    Y is more active at the start because its half-life is longer
  3. C
    X will be a hazard for longer than Y
  4. D
    both remain hazardous for the same length of time
Show answer

Answer: A. A short half-life means the activity drops quickly. A long half-life source keeps emitting radiation for a very long time, so it must be stored safely for longer.

9. Which are the products when a uranium-235 nucleus undergoes fission?

  1. A
    one helium nucleus and energy
  2. B
    a heavier nucleus and an electron
  3. C
    two smaller nuclei of roughly equal size, two or three neutrons, and gamma rays
  4. D
    a single uranium-236 nucleus
Show answer

Answer: C. The nucleus splits into two smaller daughter nuclei, releasing two or three neutrons and energy, some carried by gamma rays. U-236 is only the brief step before it splits.

10. A detector near a source records 530 counts per minute. The background count-rate is 30 counts per minute and the half-life of the source is 3 hours. What will the detector record after 9 hours?

  1. A
    62.5 counts per minute
  2. B
    66 counts per minute
  3. C
    92.5 counts per minute
  4. D
    125 counts per minute
Show answer

Answer: C. Source only: 530 − 30 = 500. Nine hours is 3 half-lives: 500 → 250 → 125 → 62.5. The detector also picks up background: 62.5 + 30 = 92.5.

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Ways to practise this chapter

Atomic structure: questions students ask

How many Atomic structure MCQs are there?

34, each with the answer and a short explanation, across 3 topics: Atoms, isotopes and the development of the atomic model (AQA 4.4.1), Radioactive decay, nuclear equations, half-life and contamination (AQA 4.4.2), Background radiation, uses of radiation, fission and fusion (AQA 4.4.3–4.4.4). Every chapter test draws ten of them, so you can take it many times.

Is the GCSE Physics (AQA) chapter 4 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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