Lesson 3.8.1.4

3.8.1.4 Nuclear instability Quiz: AQA Physics, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.8.1.4, Nuclear instability: 20 multiple choice questions for the AQA Physics (7408), Unit 8: Nuclear physics (A-level only), written with Revision Ninja.

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The 20 questions

  1. Which statement describes stable nuclei on a graph of N against Z?

    • Stable nuclei have N and Z equal for every element
    • Stable nuclei lie in a band, with N about equal to Z for light nuclei and N larger than Z for heavier nuclei
    • Stable nuclei have N much smaller than Z in all cases
    • Stable nuclei lie on a straight line with N equal to twice Z

  2. Which decay mode is typical of a nucleus with too many neutrons?

    • beta-minus decay, in which a neutron becomes a proton and emits an electron and an antineutrino
    • alpha decay, which emits a helium nucleus
    • electron capture only, in which a proton takes in an electron
    • beta-plus decay, in which a proton becomes a neutron

  3. Which decay modes are typical of a nucleus with too many protons?

    • beta-minus decay, which turns a neutron into a proton
    • fission into two equal halves
    • beta-plus decay or electron capture, which turn a proton into a neutron
    • gamma emission, which changes both N and Z

  4. In alpha decay, how do the mass number A and the proton number Z change?

    • A falls by 2 and Z falls by 4
    • A falls by 4 and Z falls by 2
    • A is unchanged and Z falls by 2
    • A falls by 4 and Z rises by 2

  5. In beta-minus decay, how do A and Z change?

    • A increases by 1 and Z is unchanged
    • A is unchanged and Z decreases by 1
    • A falls by 1 and Z is unchanged
    • A is unchanged and Z increases by 1

  6. What does gamma emission from an excited nucleus change?

    • Z rises by one while A stays the same
    • the number of neutrons falls by one
    • A falls by four and Z falls by two
    • only the energy state of the nucleus, with A and Z unchanged

  7. Which equation correctly represents the alpha decay of radium-226?

    • 226 88 Ra -> 222 86 Rn + 2 4 He
    • 226 88 Ra -> 222 88 Rn + 4 2 He
    • 226 88 Ra -> 222 86 Rn + 4 2 He
    • 226 88 Ra -> 226 86 Rn + 4 2 He

  8. What is the daughter nuclide of carbon-14 after beta-minus decay?

    • nitrogen-14
    • carbon-13
    • boron-14
    • nitrogen-13

  9. What is the daughter nuclide of sodium-22 after beta-plus decay?

    • neon-22
    • magnesium-22
    • fluorine-22
    • neon-21

  10. Which daughter nuclide results from electron capture by beryllium-7?

    • beryllium-6
    • boron-7
    • helium-7
    • lithium-7

  11. Technetium-99m decays by gamma emission. What is the result?

    • it becomes molybdenum-99 and emits an electron
    • it becomes technetium-98 and emits a neutron
    • it remains technetium-99 and loses energy as a gamma photon
    • it becomes ruthenium-99 by alpha emission

  12. A nucleus drops from an excited state 140 keV above its ground state. What is the energy of the gamma photon emitted?

    • 70 keV
    • 14 keV
    • 280 keV
    • 140 keV

  13. A nucleus with N = 130 and Z = 86 decays by alpha emission. What are the new values of N and Z?

    • N = 128, Z = 86
    • N = 130, Z = 84
    • N = 128, Z = 84
    • N = 126, Z = 84

  14. Which decay mode best restores stability for a neutron-rich nucleus?

    • beta-plus, converting a proton into a neutron, which raises N further
    • gamma emission, which changes neither N nor Z but raises N
    • beta-minus, converting a neutron into a proton and moving N and Z towards the stable band
    • electron capture, which lowers Z and raises N

  15. Why is an antineutrino emitted together with the electron in beta-minus decay?

    • to make the nucleus neutral in charge after decay
    • to conserve lepton number and share the energy and momentum, which is why the electron energies form a continuous spectrum
    • to carry away the charge of the electron so the nucleus stays neutral
    • because the antineutrino is a gamma photon of high energy

  16. Uranium-238 decays by alpha emission to thorium-234, which then decays by beta-minus to protactinium-234. What are the mass and proton numbers of protactinium-234?

    • A = 234, Z = 92
    • A = 230, Z = 91
    • A = 234, Z = 91
    • A = 234, Z = 90

  17. Why can a nucleus formed in alpha decay be left in an excited state?

    • the daughter nucleus may be left with excess energy, which is then released as gamma photons when it drops to the ground state
    • the daughter becomes stable immediately without any emission
    • excited nuclei form only in electron capture
    • the alpha particle is always emitted with zero energy

  18. Why do heavier stable nuclei contain more neutrons than protons?

    • the Coulomb repulsion between protons grows with Z, so extra neutrons add binding without adding charge
    • neutrons carry a stronger electric charge than protons
    • heavy nuclei contain no protons in their outer shells
    • protons are heavier than neutrons, so fewer protons are needed

  19. Uranium-238 undergoes two successive alpha decays. What is the nuclide produced?

    • radon-230
    • uranium-230
    • thorium-230
    • radium-230

  20. Sodium-22 decays by beta-plus and then by alpha. What are the final mass and proton numbers?

    • A = 18, Z = 8
    • A = 18, Z = 9
    • A = 18, Z = 10
    • A = 22, Z = 9

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