Radioactivity
All elements (=the building stones of all chemical substances - incl. biological) have nuclei that are made from protons (carrying a positive electrical charge) and neutrons (without an electrical charge). If the balance between the number of protons and neutrons is not optimal, the nucleus will be unstable, and will try to become stable by getting rid of excess protons or neutrons, or to add either to "improve" the balance. These processes to improve the balance is accompanied by different types of high energy radiation, called alpha, beta and gamma radiation, all of which are radioactive. Radioactivity is a type of ionising radiation and occurs naturally or may be a result of a nuclear reactor process.
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