Isotopes of phosphorus

Isotopes of phosphorus (₁₅P)
Standard atomic weight Ar°(P)
	30.973761998±0.000000005; 30.974±0.001 (abridged);

Phosphorus has many allotropes, including white phosphorus (left), red phosphorus (center left, center right), and violet phosphorus (right). See allotropes of phosphorus for more information.

Although phosphorus (₁₅P) has 22 known isotopes from ²⁶P to ⁴⁷P, only ³¹P is stable; Phosphorus is thus considered a monoisotopic element. ³¹P is also the only naturally occurring isotopes of phosphorus, so phosphorus is considered a mononuclidic element as well. The longest-lived radioactive isotopes are ³³P with a half-life of 25.35 days and ³²P with a half-life of 14.269 days. All others have half-lives of under 2.5 minutes, most under a second.