Astatine

Astatine (pronounced /ˈæstətiːn/ AS-tə-teen or /ˈæstətɨn/ AS-tətin) is a radioactive chemical element with the symbol At and atomic number 85. It is the heaviest of the discovered halogens. Although astatine is produced by radioactive decay in nature, due to its short half life it is found only in minute amounts. Astatine was first produced by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in 1940. Three years passed before traces of as... more

Astatine (pronounced /ˈæstətiːn/ AS-tə-teen or /ˈæstətɨn/ AS-tətin) is a radioactive chemical element with the symbol At and atomic number 85. It is the heaviest of the discovered halogens. Although astatine is produced by radioactive decay in nature, due to its short half life it is found only in minute amounts. Astatine was first produced by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in 1940. Three years passed before traces of astatine were also found in natural minerals. Until recently most of the physical and chemical characteristics of astatine were inferred from comparison with other elements. Some astatine isotopes are used as alpha-particle emitters in science applications, and medical applications for astatine 211 have been tested. Astatine is currently the rarest naturally-occurring element, with less than an ounce estimated to be contained in the entire Earth's crust. This highly radioactive element has been confirmed by mass spectrometers to behave... less