Astatine: Difference between revisions
imported>Milton Beychok m (Added a lede (which was absent), expanded the electron configuration in the infobos, corrected the broken reference linik, edited the History section a bit.) |
imported>Ro Thorpe (readded Greek---these youngsters, with no respect for learning...) |
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'''Astatine''' is a [[Chemical elements|chemical element]], having the [[chemical symbol]] At. Its [[atomic number]] (the number of [[proton]]s) is 85. It has a [[Atomic mass#Standard atomic weights of the elements|standard atomic weight]] of 210 g•mol<sup> −1</sup> and is a [[solid]] in its elemental form. The total amount of astatine present in the earth's crust is less than 1 [[U.S. customary units|ounce]] (28 [[gram]]s). | '''Astatine''' ([[Greek|Gr.]]: άστατος, unstable) is a [[Chemical elements|chemical element]], having the [[chemical symbol]] At. Its [[atomic number]] (the number of [[proton]]s) is 85. It has a [[Atomic mass#Standard atomic weights of the elements|standard atomic weight]] of 210 g•mol<sup> −1</sup> and is a [[solid]] in its elemental form. The total amount of astatine present in the earth's crust is less than 1 [[U.S. customary units|ounce]] (28 [[gram]]s). | ||
Astatine is considered a member of the "Halogen" class of elements. At a [[pressure]] of 101.325 k[[Pascal (unit)|Pa]], it has a [[boiling point]] of ~340 °[[Celsius (unit)|C]] and a [[melting point]] of 302 °C. | Astatine is considered a member of the "Halogen" class of elements. At a [[pressure]] of 101.325 k[[Pascal (unit)|Pa]], it has a [[boiling point]] of ~340 °[[Celsius (unit)|C]] and a [[melting point]] of 302 °C. | ||
Revision as of 19:21, 2 May 2011
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Astatine (Gr.: άστατος, unstable) is a chemical element, having the chemical symbol At. Its atomic number (the number of protons) is 85. It has a standard atomic weight of 210 g•mol −1 and is a solid in its elemental form. The total amount of astatine present in the earth's crust is less than 1 ounce (28 grams).
Astatine is considered a member of the "Halogen" class of elements. At a pressure of 101.325 kPa, it has a boiling point of ~340 °C and a melting point of 302 °C.
History
Astatine was first synthesized in 1940 by D.R. Corson, K.R. MacKenzie, and E. Segre at the University of California by bombarding bismuth with alpha particles. The longest-lived isotopes, with naturally occurring uranium and thorium isotopes, and traces of 217At are equilibrium with 233U and 239Np resulting from integration of thorium and uranium with naturally produced neutrons.
Production
Astatine can be produced by bombarding bismuth with energetic alpha particles to obtain the relatively long-lived 209-211At, which can be distilled from the target by heating in air.
Chemistry
The "time of flight" mass spectrometer has been used to confirm that this highly radioactive halogen behaves chemically very much like other halogens, particularly iodine. Astatine is said to be more metallic than iodine, and, like iodine, it probably accumulates in the thyroid gland. Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams to identify and measure elementary reactions involving astatine.
References
This article was sourced from Los Alamos National Labs on 27 June, 2008.