astatine
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as·ta·tine
(ăs′tə-tēn′, -tĭn)n. Symbol At
A highly unstable radioactive element, the heaviest of the halogen group, 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 Periodic Table.
[Greek astatos, unstable; see astasia + -ine.]
astatine
(ˈæstəˌtiːn; -tɪn)n
(Elements & Compounds) a radioactive element of the halogen series: a decay product of uranium and thorium that occurs naturally in minute amounts and is artificially produced by bombarding bismuth with alpha particles. Symbol: At; atomic no: 85; half-life of most stable isotope, 210At: 8.1 hours; probable valency: 1,3,5, or 7; melting pt: 302°C; boiling pt: 337°C (est)
[C20: from Greek astatos unstable (see astatic) + -ine2]
as•ta•tine
(ˈæs təˌtin -tɪn)n.
a rare element of the halogen family. Symbol: At; at. no.: 85.
[1945–50; < Greek ástat(os) unstable + -ine2]
as·ta·tine
(ăs′tə-tēn′) Symbol At A highly unstable, radioactive element that is the heaviest of the halogen elements. The most stable of its many isotopes has a half-life of only about eight hours. Atomic number 85. See Periodic Table.
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| Noun | 1. |  astatine - a highly unstable radioactive element (the heaviest of the halogen series); a decay product of uranium and thoriumchemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter halogen - any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions |