<P> Radioactive decay ( also known as nuclear decay or radioactivity ) is the process by which an unstable atomic nucleus loses energy ( in terms of mass in its rest frame ) by emitting radiation , such as an alpha particle , beta particle with neutrino or only a neutrino in the case of electron capture , gamma ray , or electron in the case of internal conversion . A material containing such unstable nuclei is considered radioactive . Certain highly excited short - lived nuclear states can decay through neutron emission , or more rarely , proton emission . </P>
<P> Radioactive decay ( also known as nuclear decay or radioactivity ) is the process by which an unstable atomic nucleus loses energy ( in terms of mass in its rest frame ) by emitting radiation , such as an alpha particle , beta particle with neutrino or only a neutrino in the case of electron capture , gamma ray , or electron in the case of internal conversion . A material containing such unstable nuclei is considered radioactive . Certain highly excited short - lived nuclear states can decay through neutron emission , or more rarely , proton emission . </P>
the spontaneous emission of radiation by a nucleus is known as
the spontaneous emission of radiation by a nucleus is known as
Radioactive decay ( also known as nuclear decay or radioactivity
Radioactive decay ( also known as nuclear decay or radioactivity