Astatine 85 At [210]   Switch element to... actinium aluminium aluminum americium antimony argon arsenic astatine barium berkelium beryllium bismuth bohrium boron bromine cadmium caesium calcium californium carbon cerium cesium chlorine chromium cobalt copper curium darmstadtium dubnium dysprosium einsteinium erbium europium fermium fluorine francium gadolinium gallium germanium gold hafnium hassium helium holmium hydrogen indium iodine iridium iron krypton lanthanum lawrencium lead lithium lutetium magnesium manganese meitnerium mendelevium mercury molybdenum neodymium neon neptunium nickel niobium nitrogen nobelium osmium oxygen palladium phosphorus platinum plutonium polonium potassium praseodymium promethium protactinium radium radon rhenium rhodium roentgenium rubidium ruthenium rutherfordium samarium scandium seaborgium selenium silicon silver sodium strontium sulfur sulphur tantalum technetium tellurium terbium thallium thorium thulium tin titanium tungsten ununbium ununhexium ununoctium ununpentium ununquadium ununtrium uranium vanadium xenon ytterbium yttrium zinc zirconium Go adjacent... Te I Xe Po At Rn Uuh   Uuo

The essentials

Description 

Here is a brief description of astatine.

• Standard state: solid at 298 K
• Colour: metallic
• Classification: Semi-metallic
• Availability:

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.

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.

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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