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 fromProf James Marshall's (U. North Texas, USA)Walking Tour of the elements CD.
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of astatine where known.
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 isotope20983Bi 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 + 210n
The211At 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.
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
Melting point: 575 [302 °C (576 °F)] K
Boiling point: 503 [230 °C (446 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Atomic radius (empirical): (no data) pm
Molecular single bond covalent radius: 147 (coordination number 1) ppm
van der Waals radius: [ 288 ] ppm
Pauling electronegativity: 2.2 (Pauling units)
Allred Rochow electronegativity: 1.90 (Pauling units)
Mulliken-Jaffe electronegativity: 2.85 (14.3% s orbital)
First ionisation energy: 899.00 kJ mol‑1
Second ionisation energy: 1725 kJ mol‑1
Third ionisation energy: 2565 kJ mol‑1
Universe: (no data) ppb by weight
Crustal rocks: (no data) ppb by weight
Human: (no data) ppb by weight
