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This discovery was later shown to be an erroneous one. The claimed discovery in 1931 at the Alabama Polytechnic Institute (now Auburn University) by Fred Allison and associates, led to the spurious name for the element as alabamine (Ab) for a few years. The unknown substance was called Eka-iodine before its discovery because the name of the element was to be suggested by the discoverer.

Corson, Kenneth Ross MacKenzie, and Emilio Segrè at the University of California, Berkeley by bombarding bismuth with alpha particles.Īs the periodic table of elements was long known, several scientists tried to find the element following iodine in the halogen group. Astatine (after Greek αστατος astatos, meaning "unstable") was first synthesized in 1940 by Dale R. The existence of "eka-iodine" had been predicted by Dmitri Mendeleev. Astatine is the least reactive of the halogens, being less reactive than iodine. Astatine can also react with hydrogen to form astatane, which when dissolved in water, forms the exceptionally strong hydroastatic acid. Astatine is expected to form ionic bonds with metals such as sodium, like the other halogens, but it can be displaced from the salts by lighter, more reactive halogens. Thus, following the trend, astatine would be expected to be a nearly black solid, which, when heated, sublimes into a dark, purplish vapor (darker than iodine). The halogens get darker in color with increasing molecular weight and atomic number. The final products of the decay of astatine are isotopes of lead. Its most stable isotope has a half-life of around 8.3 hours. Researchers at the Brookhaven National Laboratory have performed experiments that have identified and measured elementary reactions that involve astatine however, chemical research into astatine is limited by its extreme rarity, which is a consequence of its extremely short half-life. This highly radioactive element has been confirmed by mass spectrometers to behave chemically much like other halogens, especially iodine (it would probably accumulate in the thyroid gland like iodine), though astatine is thought to be more metallic than iodine. Astatine is currently the rarest naturally-occurring element, with less than 30g estimated to be contained in the entire Earth's crust. Some astatine isotopes are used as alpha-particle emitters in science applications, and medical applications for astatine 211 have been tested. Until recently most of the physical and chemical characteristics of astatine were inferred from comparison with other elements.

Three years passed before traces of astatine were also found in natural minerals. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in 1940. Although astatine is produced by radioactive decay in nature, due to its short half life it is found only in minute amounts. It is the second-heaviest of the discovered halogens. Astatine is a radioactive chemical element with the symbol At and atomic number 85.