What is the process called that involves the emission of ionising radiation from atomic nuclei?

The process involving the emission of ionising radiation from atomic nuclei is known as radioactivity. This phenomenon occurs when unstable nuclei of atoms decay by releasing energy in the form of radiation. This emission can include alpha particles, beta particles, or gamma rays, which are all types of ionising radiation.

Radioactivity is a natural process that occurs in certain isotopes that are not stable. These unstable isotopes undergo spontaneous decay, leading to the transformation of the nucleus and often resulting in the formation of new elements or isotopes. This concept is fundamental in understanding nuclear physics and the behavior of different elements in terms of their stability and radioactive properties.

In contrast, fission refers to the splitting of a heavy nucleus into lighter nuclei, usually accompanied by the release of energy, while fusion is the process where light nuclei combine to form a heavier nucleus, also releasing energy in the process. Transmutation involves changing one element into another, which can occur through radioactive decay but is distinct from the process specifically described by radioactivity. Radioactivity is therefore unique in its focus on the spontaneous emission of radiation from atomic nuclei.