Bismuth

Chemical element with the symbol Bi and the atomic number 83; Bismuth was considered the heaviest stable chemical element until the radioactivity of the isotope ²⁰⁹Bi was discovered in 2003. The naturally occurring Bismuth consists entirely of ²⁰⁹Bi, which has a very long half-life (about 19 quintillion years). Therefore, its specific activity is very low and cannot be detected with normal measuring devices. It decays via alpha decay to the stable Thallium isotope ²⁰⁵Tl. The Bismuth isotopes ²¹⁰Bi, ²¹¹Bi, ²¹²Bi and ²¹⁴Bi are members of the three natural decay chains (so-called radiogenic radionuclides) and therefore always exist in traces in the environment.