Astatine is a chemical element with the symbol At and atomic number 85. It is a member of the halogens, a group of elements in Group 17 of the periodic table, which also includes fluorine, chlorine, bromine, and iodine. Astatine is the rarest naturally occurring halogen and is highly radioactive, with no stable isotopes. Its most stable isotope, astatine-210, has a half-life of about 8.1 hours.
New to topics? Read the docs here!