| LC control no. | sh 85008844 |
|---|---|
| LC classification | QD181.A8 General and inorganic chemistry QD412.A8 Organometallic chemistry |
| Topical heading | Astatine |
| Variant(s) | Alabamine Anglo-helvetium Eka-iodine |
| See also | Halogens Radioactive substances |
| Found in | Wikipedia, Aug. 20, 2012 (Astatine is a radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth only as the result of the radioactive decay of certain heavier elements. All of its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Element category: halogen; sometimes classified as a metalloid (disputed). History: In 1869, when Dmitri Mendeleev published his periodic table, the space under iodine was empty; after Niels Bohr established the physical basis of the classification of chemical elements, it was suggested that the fifth halogen belonged there. Before its officially recognized discovery, it was called "eka-iodine". The first claimed discovery of eka-iodine was made by Fred Allison and his associates at the Alabama Polytechnic Institute (now Auburn University) in 1931. The discoverers named element 85 "alabamine", and assigned it the symbol Ab, designations that were used for a few years afterward.) Chemicool website, Aug. 20, 2012 (Astatine. Astatine is a halogen and a nonmetal. The first periodic table, produced by Dmitri Mendeleev in 1869, had a space directly underneath iodine. The element to fill this space became known as eka-iodine. Astatine is highly radioactive and is only available in tiny quantities. Its properties are inferred from its position in the periodic table and by studying its chemistry in extremely dilute solutions. Like the other halogens, astatine would be expected to form salts with metals such as sodium. Astatine can also react with hydrogen to form hydrogen astatide, which when dissolved in water, forms hydroastatic acid. Astatine is the least chemically reactive of the halogens and exhibits the most metallic properties of the halogen group.) Wiktionary, Aug. 20, 2012: astatine (A highly radioactive chemical element (symbol At), one of the halogens, with atomic number 85. Synonyms: alabamine (proposed name); anglo-helvetium (formerly)) alabamine ((obsolete) Former name for chemical element astatine.) |
 |  |  |