astatine (_{85}at) has 39 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 229. there also exist 23 metastableexcited states. the longest-lived isotope is ^{210}at, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is ^{219}at with a half-life of 56 seconds.

Astatine (_{85}At) has 39 known isotopes, all of which are radioactive; the range of their mass numbers is from 191 to 229. There also exist 23 metastableexcited states. The longest-lived isotope is ^{210}At, which has a half-life of 8.1 hours; the longest-lived isotope existing in naturally occurring decay chains is ^{219}At with a half-life of 56 seconds.