| From Wikipedia, the free encyclopediaAstatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. | |||
Astatine in the periodic table | |||
|---|---|---|---|
| Symbol | At | ||
| Atomic number | 85 | ||
| Group | 17 | ||
| Period | 6 | ||
| Block | p | ||
| Element category | Metalloid | ||
Physical properties | |||
| Phase at STP | Solid | ||
| Density | 6.35 g/cm3 | ||
| Atomic weight | 210 u | ||
| Melting point | 575 K 301.85 °C 575.33 °F | ||
| Boiling point | 610 K 336.85 °C 638.33 °F | ||
Atomic properties | |||
| Electronegativity (Pauling Scale) | 2.2 | ||
| Electron affinity | 233 kJ/mol | ||
| Oxidation states | −1, +1, +3, +5, +7 () | ||
| Ionization energies |
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Electron configuration | |||
| Elektronkonfiguration (shorthand) | [Xe] 4f14 5d10 6s2 6p5 | ||
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5 | ||
| Electrons per shell | 2, 8, 18, 32, 18, 7 | ||
History | |||
| Discovered | 1940 | ||
| Discovered by | Dale R. Corson Kenneth Ross MacKenzie Emilio Segrè | ||