Phosphorus (P) has 23 known isotopes with a mass number ranging from 24 to 46. Only one is stable, P-31, making phosphorus a monoisotopic element.

Longer-lived phosphorus radioisotopes are phosphorus 33 (P-33) (half-life of 25.34 days) and phosphorus 32 (P-32) (14.263 days). All other isotopes have a half-life of less than 2.5 minutes, and most of them less than one second.

Phosphorus 32 (P-32) is the phosphorus isotope whose nucleus consists of 15 protons and 17 neutrons. It disintegrates by emitting a β- (1.71 MeV) particle in 32S with a half-life of 14.263 days. It is an artificial radioactive substance obtained by neutron bombardment of stable phosphorus.

Phosphorus 32 is a high-energy beta- pure emitter, the continuous spectrum of which has a maximum energy of 1.7 MeV and an average energy of 0.7 MeV.

Phosphorus 32 is one of the most commonly used research emitters and is the one with the highest energy. Its use in molecular biology has become widespread by the use of specific high-activity nucleotides to mark DNA.

Phosphorus 32 may also be used in phosphorylation reactions. More precisely, it is used in the study of the migration of fertilizers (phosphates) in soils.

In the medical field, phosphorus-32 has been used for the treatment of polyglobulia, but this is increasingly rare.