Astatine
chemical element with symbol At and atomic number 85 / From Wikipedia, the free encyclopedia
Astatine is a radioactive, chemical element. Its atomic number is 85, and its atomic weight is 210. It is part of the Group 17 (halogens) on the periodic table of elements. All of astatine's isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.3 hours.