The process you are referring to is called nuclear decay or radioactive decay. In nuclear decay, a parent atom spontaneously undergoes a transformation and emits radiation in the form of particles or electromagnetic waves. This transformation results in the formation of daughter nuclei and, in some cases, the release of additional particles such as helium atoms (also known as alpha particles). There are different types of radioactive decay, including alpha decay, beta decay, gamma decay, and others, each involving specific particles emitted during the process.