The mass of one of its atoms given in atomic mass units. It is roughly similar to the number of protons and neutrons in an atom (the mass number) or to the average number allowing for relative isotope abundances.

The spontaneous disintegration of atomic nuclei which causes the emission of ionizing radiation or particles.

The emission of energy as electromagnetic waves or moving subatomic particles, particularly high-energy particles that produce ionization.

A radioactive process in which an atom's nucleus emits an alpha particle, lowering its atomic number by two.

The radioactive decay in which an electron is emitted

The form of radioactivity in which some unstable atomic nuclei waste excess energy by a spontaneous electromagnetic process

an energy-releasing nuclear reaction in which a heavy nucleus divides spontaneously or on collision with another particle.

a nuclear reaction in which low-atomic-number nuclei combine to generate a heavier nucleus, releasing energy in the process.

the amount of time it takes for half of a radioactive sample's atomic nuclei to decay

a stable subatomic particle that may be found in all atomic nuclei and have a positive electric charge equal to that of an electron but with the opposite sign.

subatomic particles having a mass similar to that of a proton but no electric charge. They are found in all atomic nuclei except those of common hydrogen.