The
nuclei of the atoms in some elements are unstable and emit radiation.
They are said to be radioactive.
The radiation is of three main types. We now know what these radiations are, but the French scientist Becquerel who first discovered radioactivity didn't know, and named the three types of radiation with three letters of the Greek alphabet: α (alpha), β (beta) and γ (gamma).
We now know that :
Alpha
radiation is relatively slow-moving helium nuclei; they are positively
charged and called alpha particles- Beta radiation is fast moving electrons; they are negatively charged and called beta particles. These electrons have not come from the electron shells around the nucleus. Instead, they form when a neutron within the nucleus splits into a proton and an electron.
- Gamma radiation is high-energy electromagnetic waves; these waves are of very short wavelength i.e. (high frequency). It is often referred to as gamma rays and has the same nature as X-rays.
Radioactive nuclei carry on giving out these radiations whatever is happening in their surroundings, e.g. chemical reactions or change of temperature. The radiations transfer energy from the nucleus and ionise the substances they pass through.
Radioactive elements are found naturally in the environment. The radiation these give off is called background radiation.
[ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science
]