Bismuth-209

EN Texto em inglês Ainda não há artigo no teu idioma: trecho em inglês.

Bismuth-209 (Bi) is an isotope of bismuth with the longest known half-life of any nuclide that undergoes α-decay (alpha decay); the decay product is thallium-205. It has 83 protons and a magic number of 126 neutrons, and naturally occurring bismuth consists entirely of this isotope. Bismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, a research team at the Institut d'astrophysique spatiale in Orsay, France, discovered that Bi undergoes alpha decay with a half-life now given more precisely as 2.01×10 years (20.1 quintillion years), over 10 times longer than the estimated age of the universe. The heaviest nucleus considered to be stable is now lead-208 and the heaviest stable monoisotopic element is gold (gold-197). Theory had previously predicted a half-life of 4.6×10 years. It had been suspected to be radioactive for a long time. The decay produces a 3.14 MeV alpha particle plus thallium-205. Due to its extremely long half-life, Bi can be treated as non-radioactive for nearly all applications. It is much less radioactive than human flesh, so it poses no real radiation hazard. Though Bi holds the half-life record for alpha decay, it does not have the longest known half-life of any nuclide; this distinction belongs to tellurium-128 (Te) with a half-life estimated at 7.7×10 years by double beta decay.