Radioactivity is the random spontaneous disintegration of an atom of an element. The stability of the nucleus depends on the relative numbers of protons and neutrons present. The most stable nuclides tend to have an even number of protons and an even number of neutrons as each group of two protons and two neutrons, in the nucleus, makes an especially stable combination. A number of elements have atoms or nuclei which are unstable and consequently split up to form smaller atoms. This is due to all elements wanting to achieve equilibrium or stability in the nucleus.

A substance is said to be radioactive if it contains unstable nuclei and is able to naturally release energy in the process of shedding high speed charged particles, in an attempt to reach a stable state. With this, a non-radioactive substance will remain intact indefinitely unless acted upon by an external force.

In the process of transmutation, known as decay, the radioactive nuclei emits charged particles or electromgnetic rays depending on the nature it's instability. This results in a daughter nuclide being produced which may be radioactive or stable, but if it is radioactive it will in turn decay into a daughter nuclide, continuing to do so until it reaches the point of stability, an isotope of lead.

Contents page.

ANDREW SIDELL / June 2002 / as0904@bristol.ac.uk