a radioactive chemical element, one of the halogens, formed from bismuth when it is bombarded by alpha particles: it resembles iodine in its chemical properties: symbol, At; at. no., 85
< Gr astatos, unstable + -ine
See astatine in American Heritage Dictionary 4
noun Symbol At
A highly unstable radioactive element, the heaviest of the halogen series, that resembles iodine in solution. Its longest lived isotope has a mass number of 210 and has a half-life of 8.3 hours. Atomic number 85; melting point 302°C; boiling point 337°C; valence probably 1, 3, 5, 7. See Table at element.