Explain what happens to the nucleus of an atom during alpha decay.

WJEC GCSE Physics (Wales) — 2.9 Nuclear decay and nuclear energy · Explain · 4 marks · View as Markdown

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

Radioactive decay is a process in which an unstable nucleus loses energy by emitting radiation. Alpha decay is one type of radioactive decay.

Model answer (4 marks)

The nucleus emits an alpha particle, which is a helium nucleus consisting of 2 protons and 2 neutrons. Consequently, the atomic number of the nucleus decreases by 2 and the mass number decreases by 4.

Examiner tips

Use the phrase "emits an alpha particle" to show the process.
State the composition of the alpha particle (2p, 2n).
Explain the changes in atomic and mass numbers.
Keep the answer concise and use correct terminology.

Common mistakes

Failing to mention the alpha particle’s composition.
Using the word "neutron" instead of "nucleon" for the mass change.
Not specifying the decrease in atomic number or mass number.

Mark scheme (4 marks)

The nucleus emits an alpha particle
An alpha particle consists of 2 protons and 2 neutrons
The atomic number (proton number) of the nucleus decreases by 2
The mass number (nucleon number) of the nucleus decreases by 4

Key terms in this question

alpha decay · nucleus