A radioactive source emits beta particles. Explain what a beta particle is and describe how beta emission changes the nucleus of the atom from which it is released.

WJEC GCSE Physics (Wales) — 2.4 The atom, the nucleus and radioactivity · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A beta particle is a fast‑moving electron emitted from the nucleus.
During beta emission a neutron in the nucleus changes into a proton and releases a beta particle.
The atomic number of the atom increases by one.
The mass number remains unchanged.

Examiner tips

  • Use the term ‘beta particle’ and state it is an electron. Explain the neutron→proton conversion. Mention the increase in atomic number and that the mass number stays the same.
  • common_mistakes
  • :
  • Calling the beta particle a positron (wrong charge). Forgetting that the mass number does not change.

Mark scheme (4 marks)

  1. A beta particle is a fast-moving electron (emitted from the nucleus)
  2. A neutron changes into a proton (and a beta particle) during beta emission
  3. The atomic number (proton number) increases by one
  4. The mass number (nucleon number) stays the same / is unchanged

Key terms in this question

beta particle · nucleus

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