Phosphorus-31

Main isotopes of phosphorus

iso NA half-life DM DE (MeV) DP 31P 100% is stable with 16 neutrons 32P trace 14.28 d β− 1.709 32S 33P trace 25.3 d β− 0.249 33S
Standard atomic weight (Ar)	7001309737619980000♠30.973761998(5)

Although phosphorus (₁₅P) has 23 isotopes from ²⁴P to ⁴⁶P, only one of these isotopes is stable ³¹P; as such, it is considered a monoisotopic element. The longest-lived radioactive isotopes are ³³P with a half-life of 25.34 days and ³²P with a half-life of 14.263 days. All other have half-lives under 2.5 minutes, most under a second. The least stable is ²⁵P with a half-life shorter than 30 nanoseconds—the half-life of ²⁴P is unknown.

³²P, a beta-emitter (1.71 MeV) with a half-life of 14.3 days, is used routinely in life-science laboratories, primarily to produce radiolabeled DNA and RNA probe, e.g. for use in Northern blots or Southern blots. Because the high-energy beta particles produced penetrate skin and corneas, and because any ³²P ingested, inhaled, or absorbed is readily incorporated into bone and nucleic acids, OSHA requires that a lab coat, disposable gloves, and safety glasses or goggles be worn when working with ³²P, and that working directly over an open container be avoided in order to protect the eyes. personal, clothing, and surface contamination is also required. In addition, due to the high energy of the beta particles, shielding this radiation with the normally used dense materials (e.g. lead), gives rise to secondary emission of X-rays via a process known as bremsstrahlung, meaning braking radiation. Therefore, shielding must be accomplished with low-density materials, e.g. Plexiglas, Lucite, plastic, wood, or water.

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