Isotopes of polonium

Polonium (₈₄Po) has 33 isotopes, all of which are radioactive, with between 186 and 227 nucleons. ²¹⁰Po with a half-life of 138.376 days has the longest half-life of naturally occurring polonium. ²⁰⁹Po with a half-life of 125 years has the longest half-life of all isotopes of polonium. ²⁰⁹Po and ²⁰⁸Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron.

Polonium-210

²¹⁰Po is an alpha emitter that has a half-life of 138.376 days; it decays directly to stable ²⁰⁶Pb. A milligram of ²¹⁰Po emits as many alpha particles per second as 5 grams of ²²⁶Ra.^[2] A few curies (1 curie equals 37 gigabecquerels) of ²¹⁰Po emit a blue glow caused by excitation of surrounding air. A single gram of ²¹⁰Po generates 140 watts of power.^[3] Because it emits many alpha particles, which are stopped within a very short distance in dense media and release their energy, ²¹⁰Po has been used as a lightweight heat source to power thermoelectric cells in artificial satellites; for instance, a ²¹⁰Po heat source was also in each of the Lunokhod rovers deployed on the surface of the Moon, to keep their internal components warm during the lunar nights.^[4] Some anti-static brushes, used for neutralizing static electricity on materials like photographic film, contain a few microcuries of ²¹⁰Po as a source of charged particles.^{[5] 210}Po is also used in initiators for atomic bombs through the (α,n) reaction with beryllium.

The majority of the time ²¹⁰Po decays by emission of an alpha particle only, not by emission of an alpha particle and a gamma ray. About one in 100,000 decays results in the emission of a gamma ray.^[6] This low gamma ray production rate makes it more difficult to find and identify this isotope. Rather than gamma ray spectroscopy, alpha spectroscopy is the best method of measuring this isotope.

²¹⁰Po occurs in minute amounts in nature, where it is an intermediate isotope in the uranium series decay chain. It is generated via beta decay from ²¹⁰Bi.

²¹⁰Po is extremely toxic, with one microgram being enough to kill the average adult (250,000 times more toxic than hydrogen cyanide by weight).^{[7] 210}Po was used to kill Russian dissident and ex-FSB officer Alexander V. Litvinenko in 2006,^[8] and was suspected as a possible cause of Yasser Arafat's death, following exhumation and analysis of his corpse in 2012–2013.^[9]

List of isotopes

1. ↑ Abbreviations:
   EC: Electron capture
   IT: Isomeric transition
2. ↑ Bold for stable isotopes, bold italics for nearly stable isotopes (half-life longer than the age of the universe)
3. 1 2 3 Intermediate decay product of Uranium-238
4. 1 2 Intermediate decay product of Uranium-235
5. 1 2 Intermediate decay product of Thorium-232

Notes

• Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
• Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
• Half-life abbreviations are y=year, d=day, min=minute, s=second, ms=millisecond, µs=microsecond, ns=nanosecond.
• A superscripted m (or m2, etc.) refers to an isomer of that particular isotope.

References