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 8.1 hours.
History[change | change source]
The first creation of the element was in 1940 by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio G. Segrè at the University of California, Berkeley, who named it from the Greek astatos (ἄστατος), meaning "unstable".
Chemistry[change | change source]
Some of its isotopes may be found in nature. But because it is extremely unstable, only about an ounce exists in the Earth's crust at one point in time. The longest-living isotope 210At has a half-life of a bit over eight hours. Chemists say it is the rarest element in the earths crust. Astatine is an extremely radioactive element and all its isotopes have half-lives of 8.1 hours or less. Less reactive than iodine, astatine is the least reactive of the halogens. Only a few compounds with metals have been found, in the form of astatides of sodium, palladium, silver, thallium, and lead.
Uses[change | change source]
It can be used for cancer treatment and in radioactive tracers.