Astatine is a chemical element in the periodic table that has the symbol At and atomic number 85. This radioactive element occurs naturally from uranium and thorium decay and is the heaviest of the halogens.

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.

Reference

Los Alamos National Laboratory - Astatine

External links

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Element 85".