Astatine: the essentials
The longest-lived isotope, 210At, has a half-life of only 8.3 hours. There are about 20 isotopes known, all of which are radioactive. Astatine is a halogen and possibly accumulates in the thyroid like iodine.
This sample of uranite contains a vanishingly small amount of astatine. Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Astatine: historical information
Astatine ynthesized in 1940 by Dale Corson and others at the University of California, USA, by bombarding bismuth (209Bi) with α-particles.
Astatine around us Read more »
Astatine has no biological role.
Astatine is not found in any significant quantity in the geosphere. Some isotopes of astatine (215At, 218At and 219At) are present in uranium and thorium minerals as part of radiodecay series. The total amount present in the Earth's crust is probably less than 30 g at any one time.
|Location||ppb by weight||ppb by atoms||Links|
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|Human||(no data) ppb by weight||(no data) atoms relative to C = 1000000|
Physical properties Read more »
- Density of solid: 6400 (estimated) kg m-3
- Molar volume: 33 (rough estimate based upon density estimate) cm3
- Thermal conductivity: 1.7 (estimate) W m‑1 K‑1
Heat properties Read more »
- Melting point: 575 [302 °C (576 °F)] K
- Boiling point: 503 [230 °C (446 °F)] K
- Enthalpy of fusion: about 6 (per mol At atoms) kJ mol-1
Crystal structure Read more »
The solid state structure of astatine is: .
Astatine: orbital properties Read more »
Astatine atoms have 85 electrons and the shell structure is 22.214.171.124.18.7. The ground state electronic configuration of neutral Astatine is [Xe].4f14.5d10.6s2.6p5 and the term symbol of Astatine is 2P3/2.
- Pauling electronegativity: 2.2 (Pauling units)
- First ionisation energy: 920 kJ mol‑1
- Second ionisation energy: (no data) kJ mol‑1
Isolation: astatine is radioactive and essentially unavailable in nature. It is not possible to make other than in a nuclear reactor. Bombardment of the bismuth isotope 20983Bi with α-particles (helium nuclei, 42He) results in formation of shortlived astatine and neutrons. The bismuth target is cooled during irradiation to prevent the volatile astatine disappearing.
20983Bi + 42He → 21185At + 2 10n
The 211At isotope has a half life of just over 7 hours so it is necessary to work quickly with it! Available quantities are of the order of 0.001 mg.
Heating the bismuth target to 300-600°C under N2 results in a stream of the elemental astatine that can be collected on a cold glass finger.
Astatine isotopes Read more »