|
Seldom found in nature.
| Atomic Number: |
85 |
| Atomic Symbol: |
At |
| Atomic Weight: |
210 |
| Electron Configuration: |
[Xe]6s24f145d106p5 |
History
(Gr. astatos, unstable) 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. The total amount of astatine present in the
earth's crust, however, is less than 1 oz.
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.
Properties
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.
|
