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.

Table: basic information about and classifications of astatine.

Astatine: historical information

Astatine was discovered by Dale Corson, MacKenzie, Segre at 1940 in California, USA. Origin of name: from the Greek word "astatos" meaning "unstable".

Astatine ynthesized in 1940 by Dale Corson and others at the University of California, USA, by bombarding bismuth (209Bi) with α-particles.

Astatine: physical properties

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Astatine: orbital properties

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Isolation

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.

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astatine atomic number