The division of chemistry dealing with changes in or transformations of the
atomic nucleus. It includes spontaneous and induced radioactivity, the fission or
splitting of nuclei, and their fusion, or union; also the properties and behaviour of the
reaction products and their separation and analysis. The reactions involving nuclei are
usually accompanied by large energy changes, far greater than those of chemical reactions;
that are carried out in nuclear reactors for electric power production and manufacture of
radioactive isotopes for medical use, also (in research work) in cyclotrons.