| General | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Name, Symbol, Number | Astatine, At, 85 | ||||||||||||
| Series | Halogens | ||||||||||||
| Group, Period, Block | 17 (VIIA), 6 , p | ||||||||||||
| Density, Hardness | no data, no data | ||||||||||||
| Appearance | metallic | ||||||||||||
| Atomic Properties | |||||||||||||
| Atomic weight | [210] amu | ||||||||||||
| Atomic radius | no data | ||||||||||||
| Covalent radius | 127 pm | ||||||||||||
| van der Waals radius | no data | ||||||||||||
| Electron configuration | [Xe]44f14 5d10 6s2 6p5 | ||||||||||||
| e- 's per energy level | 2, 8, 18, 32, 18, 7 | ||||||||||||
| Oxidation states (Oxide) | ±1,3,5,7 (unknown) | ||||||||||||
| Crystal structure | no data | ||||||||||||
| Physical Properties | |||||||||||||
| State of matter | solid | ||||||||||||
| Melting point | 575 K (576 °F) | ||||||||||||
| Boiling point | no data | ||||||||||||
| Molar volume | no data | ||||||||||||
| Heat of vaporization | no data | ||||||||||||
| Heat of fusion | 114 kJ/mol | ||||||||||||
| Vapor pressure | no data | ||||||||||||
| Speed of sound | no data | ||||||||||||
| Miscellaneous | |||||||||||||
| Electronegativity | 2.2 (Pauling scale) | ||||||||||||
| Specific heat capacity | no data | ||||||||||||
| Electrical conductivity | no data | ||||||||||||
| Thermal conductivity | 1.7 W/(m*K) | ||||||||||||
| 1st ionization potential | 920 kJ/mol (estimated) | ||||||||||||
| Most Stable Isotopes | |||||||||||||
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| SI units & STP are used except where noted. | |||||||||||||
Notable Characteristics
This highly radioactive element has been confirmed by mass spectrometers to behave chemically much like other halogens, especially iodine (it probably accumulates in the thyroid gland like iodine). Astatine is thought to be more metallic than iodine. Researchers at the Brookhaven National Laboratory have performed experiments that have identified and measured elementary reactions that involve astatine.
The total amount of astatine in Earth's crust is estimated to be less than 1 oz (28 g) at any one time.
History
Astatine (Greek astatos meaning "unstable") was first synthesized in 1940 by Dale Corson, K. R. MacKenzie, and Emilio Segre of the University of California, Berkeley by barraging bismuth with alpha particles.
Occurrence
Astatine is produced by bombarding bismuth with energetic alpha particles to obtain relatively long-lived At-209 - At-211, which can then be distilled from the target by heating in the presence of air.
Isotopes
Astatine has about 20 known isotopes, all of which are radioactive; the longest-lived isotope is 210At which has a half-life of only 8.3 hours. Astatine is a halogen and possibly accumulates in the thyroid like iodine.