A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess atomic energy, making it unstable. This excess energy is often utilized in one among three ways: emitted from the nucleus as gamma radiation; transferred to at least one of its electrons to release it as a conversion electron, or wont to create and emit a replacement particle (alpha particle or beta particle) from the nucleus. During those processes, the radionuclide is claimed to undergo decay. These emissions are considered radiation because they're powerful enough to liberate an electron from another atom. The decay can produce a stable nuclide or will sometimes produce a replacement unstable radionuclide which can undergo further decay. Radioactive decay may be a random process at the extent of single atoms: it's impossible to predict when one particular atom will decay.
