What is the process called when an unstable nucleus releases energy to become more stable?

The process whereby an unstable nucleus releases energy in an effort to attain a more stable state is known as nuclear decay. This phenomenon occurs naturally as unstable isotopes undergo transformations, emitting radiation in the form of alpha particles, beta particles, or gamma rays. The primary goal of nuclear decay is to reach a stable configuration, often through a series of decay steps that may involve various forms of radiation.

In contrast to other processes mentioned, nuclear fusion involves the merging of light atomic nuclei into a heavier nucleus, typically occurring in stars and requiring immense amounts of energy. Nuclear fission is the splitting of a heavy nucleus into lighter nuclei, which also releases energy but differs fundamentally from decay. Nuclear transmutation involves the conversion of one chemical element or isotope into another through nuclear reactions, which can include decay but is a broader term that encompasses various ways elements can change.