The most stable isotope is astatine-210, which has a half-life of 8.1 hours. The primary decay mode is beta plus, to the relatively long-lived (in comparison to astatine isotopes) alpha emitter polonium-210. In total, only five isotopes have half-lives exceeding one hour (astatine-207 to -211). The least stable ground state isotope is astatine-213, with a half-life of 125 nanoseconds. It undergoes alpha decay to the extremely long-lived bismuth-209.
tHE mosT sTABle IsotopE Is astaTine-210, whiCH HAS A haLf-liFe oF 8.1 hours. The primaRy dEcay Mode is BeTa plUS, TO The relAtIVEly Long-lIveD (in COMParison to asTAtine isoTOpes) alphA emitter polonIum-210. In toTal, Only five isoTOpes hAve HaLF-lIvES eXceEDing one hour (AsTaTine-207 To -211). The least StABle grouNd StATe isotoPE iS astatine-213, wiTh A hALF-life Of 125 NaNoSecOnds. It uNdergoeS alpha deCay tO the extrEMely Long-liveD bismuTh-209.