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astatine [At]
From the Greek astatos meaning unstable. First produced in 1940 by DR Corson, KR MacKenzie & E Segre at the University of California, Berkeley by bombarding a bismuth isotope with alpha particles (helium nuclei).
Occurrence:
1) rarest of 92 naturally occurring elements
2) < 30 g exists on earth at any one time
3) occurs as a natural by-product of uranium & thorium decay
Characteristics:
1) radioactive halogen element
2) solid non-metal of unknown color at room temperature
3) very radioactive; decays quickly
Uses: none
Related
periodic table
General
halogen
radioactive element
Properties
SIZE: AW = 209.99
atomic number
VALUE: 85
VALENCE: XE 4F14 5D10 6S2 6P5
References
- Webster's Ninth New Collegiate Dictionary, Miriam-
Webster Inc. Springfield, MA 1990
- Chemical & Engineering News, Sept 8, 2003