|
AstatineSeldom found in nature.
| Atomic Number: | 85 | Atomic Symbol: | At |
| Atomic Weight: | 210 | Electron Configuration: | 2-8-18-32-18-7 |
| Shells: | 2,8,18,32,18,7 | Filling Orbital: | 6p5 |
| Melting Point: | 302oC | Boiling Point: | 337oC |
| Description: | Radioactive member of the halogen group.
| | Uses: | Does not occur in nature. Similar to iodine. Produced by bombarding bismuth with alpha particles. |
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.
Isotopes
The longest-lived isotopes, with naturally occurring uranium and thorium isotopes, and traces of 217At are
equilibrium with 233U and 239Np reulting from interation of thorium and uranium with naturally produced neutrons.
Occurence
The total amount of astatine present in the earth's crust, however, is less than 1 oz.
Properties
- 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.
- 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.
Uses
Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams
to identify and measure elementary reactions involving astatine.
|
