오스뮴 (Os)

발견 과정

발견: 1804 · Smithson Tennant

Osmium was discovered in 1803 by Smithson Tennant and William Hyde Wollaston in London, England. Its discovery is intertwined with that of platinum and the other metals of the platinum group. Platinum reached Europe as platina ("small silver"), first encountered in the late 17th century in silver mines around the Chocó Department, in Colombia. The discovery that this metal was not an alloy but a new element was published in 1748. Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue. Joseph Louis Proust thought the residue was graphite. Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed iridium in the black platinum residue in 1803, but did not obtain enough material for further experiments. Later t

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Osmium is one of the least abundant stable elements in Earth's crust, with an average mass fraction of 50 parts per trillion in the continental crust. Osmium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium (iridium rich), and iridosmium (osmium rich). In nickel and copper deposits, the platinum-group metals occur as sulfides (i.e., (Pt,Pd)S), tellurides (e.g., PtBiTe), antimonides (e.g., PdSb), and arsenides (e.g., PtAs2); in all these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum-group metals, osmium can be found naturally in alloys with nickel or copper. Within Earth's crust, osmium, like iridium, is found at highest concentrations in three types of geologic structure: igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one o

동위원소

Osmium has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. At least 37 artificial radioisotopes and 20 nuclear isomers exist, with mass numbers ranging from 160 to 203; the most stable of these is 194Os with a half-life of 6.0 years. The two primordial radioisotopes 184Os and 186Os are known to undergo alpha decay, but with such long half-lives — the current best values are (1.12±0.23)×1013 and (2.0±1.1)×1015 years, approximately 140000 times the age of the universe — that for practical purposes it can be considered stable. Alpha decay is predicted for all the other naturally occurring isotopes, but has not been observed, presumably due to very long half-lives; 184Os and 192Os are also predicted to undergo double beta decay, but this not been observed either. 189Os has a spin of 3⁄2 but 187Os has a nuclear spin 1⁄2. Its