Bismuth-206

Main isotopes of bismuth

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct 207Bi syn 31.55 y β+ 207Pb 208Bi syn 3.68×105 y β+ 208Pb 209Bi 100% 1.9×1019 y α 205Tl 210Bi trace 5.012 d β− 210Po α 206Tl 210mBi syn 3.04×106 y IT 210Bi α 206Tl
Standard atomic weight (Ar)	7002208980400000000♠208.98040(1)

Bismuth (₈₃Bi) has no stable isotopes, but does have one very long-lived isotope; thus, the standard atomic weight can be given as 7002208980400000000♠208.98040(1). Although bismuth-209 is now known to be unstable, it has classically been considered to be a "stable" isotope because it has a half-life of over 1.9×10¹⁹ years, which is more than a billion (1000 million) times the age of the universe. Besides ²⁰⁹Bi, the most stable bismuth radioisotopes are ^210mBi with a half-life of 3.04 million years, ²⁰⁸Bi with a half-life of 368,000 years and ²⁰⁷Bi, with a half-life of 32.9 years, none of which occur in nature. All other isotopes have half-lives under 1 year, most under a day. Of naturally occurring radioisotopes, the most stable is radiogenic ²¹⁰Bi with a half-life of 5.012 days.

Commercially the radioactive isotope bismuth-213 can be produced by bombarding radium with bremsstrahlung photons from a linear particle accelerator. In 1997 an antibody conjugate with Bi-213, which has a 45-minute half-life, and decays with the emission of an alpha-particle, was used to treat patients with leukemia. This isotope has also been tried in cancer treatment, e.g. in the Targeted Alpha Therapy (TAT) program. Bismuth-213 is also found on the decay chain of uranium-233 which is the fuel "bred" by Thorium reactors.

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