Radioactive decay

If the nucleus is unstable it can decay in one of three ways:
(a) by emitting beta particle (a high speed electron or positron)
(b) by emitting an alpha particle (a helium nucleus)
(c) by emitting a gamma ray (short wavelength electromagnetic radiation)

Examples of the three methods of decay are:

The following diagram shows the necay of a nucleus which has N neutrons, Z protons and with a nucleon number A. Alpha, beta plus (positron) and beta minus (electron) emissions are shown.