What term describes the process when particles and rays are emitted from a nucleus?

The term that describes the process when particles and rays are emitted from a nucleus is radioactivity. This phenomenon occurs when an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. There are various types of emissions, including alpha particles, beta particles, and gamma rays, which are key aspects of radioactive decay.

Radioactivity is a natural process seen in radioactive isotopes, which spontaneously transform into different elements or isotopes while releasing energy. This characteristic distinguishes it from other processes like fusion and fission, which involve changes in the nucleus but do not necessarily involve the emission of particles or rays as a means of stabilization. In fusion, nuclei combine to form a heavier nucleus, while fission involves the splitting of a heavy nucleus into lighter nuclei, both of which release energy but do not primarily focus on the emission phenomenon central to radioactivity. Radiation, while it can refer to the energy emitted during these processes, is a broader term that includes any emitted energy, not just that from radioactive decay. Thus, radioactivity specifically defines the process in question.