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What is radioactivity?

Nuclear radiation

When an unstable nucleus decays, there are three ways that it can do so. Its nucleus may give out:

  • An alpha particle
  • A beta particle
  • It may also give out a gamma ray

Types of radiation

The table describes alpha particles and beta particles.


Type of radiationWhat is it?
Alpha particleTwo protons and two neutrons – the same as a helium nucleus
Beta particleFast-moving electron


Nuclear radiation ionises materials. Ionisation happens when:

  • Particles lose electrons and become positively charged
  • Particles gain electrons and become negatively charged

Higher tier

Ionisation can be harmful to living cells. Alpha particles are particularly good ionisers. They have a much larger mass, and a greater charge, than beta particles.

Read on if you're taking the higher paper.

Back to Radiation for life index

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