Radioactivity
Energy
transfer
Radiation is a form of energy transfer. In the nucleus of atoms there are powerful forces at work. Not always effectively. Alpha radiation occurs when the positive charge in the nucleus is too strong and an alpha particle is ejected. In other cases there are too many neutral particles and these split to release high energy electrons (beta particles). Sometimes a nucleus has too much energy and an electromagnetic pulse (gamma ray) is emitted.
Source: Galson Sciences Limited