This page provides a very brief introduction to radiation, radioactivity and nuclear energy. Radiation and Nuclear Power Fission, Fusion and Safety and Nuclear Power Developing Energy and Nuclear Power Environment and Nuclear Power Single copies of all these publications are available free on request.
All matter is made up of atoms.
The protons and neutrons combine to create the nucleus, which is the centre of an atom. However, the elements atomic mass is equal to the number of protons plus the number of neutrons. All atoms of the same element have the same number of protons, but they do not have to have the same number of neutrons. In other words, atoms of the same element can have a different atomic mass. Most elements have several isotopes.