ASTATINE

as·ta·tine   (ās'tə-tēn', -tĭn)    n.   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. [Greek astatos, unstable; see astasia + -ine2.]

Main Entry: as·ta·tine
Pronunciation: 'as-t&-"tEn
Function: noun
: a radioactive halogen element discovered by bombarding bismuth withhelium nuclei and also formed by radioactive decay —symbol At; called also ekaiodine; —see ELEMENTtable

astatine as·ta·tine (ās'tə-tēn', -tĭn)
n.
Symbol At
A radioactive halogen element. Its longest lived isotope has a mass number of 210 and a half-life of 8.1 hours. Atomic number 85; melting point 302°C; boiling point 337°C; valence probably 1, 3, 5, 7.

astatine

radioactive chemical element and the heaviest member of the halogen elements, or Group 17 (Group VIIa) of the periodic table. Astatine, which has no stable isotopes, was first synthetically produced (1940) at the University of California by American physicists Dale R. Corson, Kenneth R. MacKenzie, and Emilio Segre, who bombarded bismuth with accelerated alpha particles (helium nuclei) to yield astatine and neutrons. Naturally occurring astatine isotopes have subsequently been found in minute amounts in the three natural radioactive decay series, in which they occur by minor branching (astatine-218 in the uranium series, astatine-216 in the thorium series, and astatine-215 and astatine-219 in the actinium series). Thirty-three isotopes are known; astatine-210, with a half-life of 8.3 hours, is the longest lived.

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