What is the definition of gcse radioactivity?

Remove radiation as it changes to become more stable. There are three types of radioactivity, called alpha, beta, and gamma. A radioactive nucleus will emit an alpha particle or a beta particle or a gamma ray. After a nucleus has emitted an alpha particle or a beta particle, the atomic number of the atom will have changed.

The atom will have been transformed into a different element. An alpha or beta emitter can also emit gamma radiation. For now, for the GCSE exams, let's accept the idea that the rate of radioactive decay does not depend on external factors.