Boron-11
Boron (B) naturally occurs as isotopes, 10B and 11B, the latter of which makes up about 80% of natural boron. There are 14 radioisotopes that have been discovered, with mass numbers from 6 to 21, all with short half-lives, the longest being that of 8B, with a half-life of only 770 milliseconds (ms) and 12B with a half-life of 20.2 ms. All other isotopes have half-lives shorter than 17.35 ms, with the least stable isotope being 7B, with a half-life of 150 yoctoseconds (ys). Those isotopes with mass below 10 decay into helium (via short-lived isotopes of beryllium for 7B and 9B) while those with mass above 11 mostly become carbon.
Relative atomic mass: 10.811(7)
Boron-10 is used in boron neutron capture therapy (BNCT) as an experimental treatment of some brain cancers.
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