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astatine

[as-tuh-teen, -tin] /ˈæs təˌtin, -tɪn/
noun, Chemistry
1.
a rare element of the halogen family. Symbol: At; atomic number: 85.
Origin
1945-1950
1945-50; < Greek ástat(os) not steadfast, unstable (see astatic) + -ine2
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples from the web for astatine
  • One of his major contributions was the observation of the spectra of astatine.
British Dictionary definitions for astatine

astatine

/ˈæstəˌtiːn; -tɪn/
noun
1.
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)
Word Origin
C20: from Greek astatos unstable (see astatic) + -ine²
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for astatine
n.

radioactive element, named 1947, from Greek astatos "unstable" (see astatic) + chemical suffix -ine (2). So called for its short half-life and lack of stable isotopes. "The element appears not to have a stable form and probably does not exist in nature" [Flood, "Origin of Chemical Names"].

Online Etymology Dictionary, © 2010 Douglas Harper
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astatine in Medicine

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.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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astatine in Science
astatine
  (ās'tə-tēn')   
Symbol At
A highly unstable, rare, radioactive element that is the heaviest of the halogen elements. Its most stable isotope 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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for astatine

At

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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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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