Bismuth (83Bi) has 41 known isotopes, ranging from 184Bi to 224Bi. Bismuth has no stable isotopes, but does have one naturally occurring, very long-lived isotope; thus, the standard atomic weight can be given from that isotope, bismuth-209. Though it is now known to be radioactive, it may still be considered practically stable because it has a half-life of 2.01×1019 years, which is more than a billion 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 31.22 years, none of which occur in nature. All other isotopes have half-lives under 15 days, most under two hours. Of naturally occurring radioisotopes, the most stable is radiogenic210Bi with a half-life of 5.012 days. 210mBi is unusual for being a nuclear isomer with a half-life many orders of magnitude longer than that of the ground state.
↑ ()– Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
↑ #– Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
↑ Bold half-life– nearly stable, half-life longer than age of universe.
↑ Theoretically capable of isomeric transition to 210Bi with a partial half-life of ~5.5×1020 years or β− decay to 210Po with a partial half-life over 1013 years.[7]
↑ Theoretically capable of α decay to 211Tl; the branching ratio is expected to be ~8×10−5% (partial half-life ~18.1 y).[8]
Bismuth-213
Bismuth-213 (213Bi) has a half-life of 45.6 minutes and decays mainly by beta emission to polonium-213; with only 2.1% going via alpha emission to thallium-209; however, as the polonium instantly decays by alpha, one alpha particle is emitted per atom. The amounts needed for medical use are always produced through its decay chain (the neptunium series) from either thorium-229 (limited supply due to the long life of that isotope) or actinium-225, which can be produced directly from radium-226, for example by bombardment with bremsstrahlung photons from a linear particle accelerator, knocking out a neutron and through beta decay giving actinium-225.
In 1997, an antibody conjugate with 213Bi was used to treat patients with leukemia, and this isotope has otherwise been used in targeted alpha therapy (TAT) to treat a variety of cancers.[9]
Bismuth-213 is also produced in the decay of uranium-233, the fuel bred by thorium reactors, but as mentioned this goes through the long-lived thorium-229, so the production rates from each reactor will not be large.
↑ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3) 030003. doi:10.1088/1674-1137/abddaf.
↑ Imam, S (2001). "Advancements in cancer therapy with alpha-emitters: a review". International Journal of Radiation Oncology, Biology, Physics. 51 (1): 271–278. doi:10.1016/S0360-3016(01)01585-1. PMID11516878.
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