Astatine

Astatine: the essentials

 Brief description: 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.

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.

WebElements Shop

WebElements now has an online shop at which you can buy periodic table posters, mugs, T-shirts, games, molecular models, and more.