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Ruthenium is a chemical element in the periodic table that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys.
Notable characteristicsA polyvalent hard white metal, ruthenium is a member of the platinum group, has four crystal modifications and does not tarnish at normal temperatures, but does oxidize explosively. Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by halogens at high temperatures and by hydroxides. Small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is increased markedly by the addition of a small amount of ruthenium. This metal can be plated either through electrodeposition or by thermal decomposition methods. One ruthenium-molybdenum alloy has been found to be superconductive at 10.6 K. The oxidation states of ruthenium range from +1 to +8, and -2 is known, though oxidation states of +2, +3, and +4 are most common. ApplicationsDue to its highly effective ability to harden platinum and palladium, ruthenium is used in Pt and Pd alloys to make severe wear resistance electrical contacts.
Ruthenium is also a versatile catalyst: Hydrogen sulfide can be split by light by using an aqueous suspension of CdS particles loaded with ruthenium dioxide. This may be useful in the removal of H2S from oil refineries and from other industrial processes. Organometallic ruthenium carbene and allenylidene complexes have recently been found as highly efficient catalysts for olefin metathesis (= redistribution of olefinic =CRR' groups) with important applications in organic and pharmaceutical chemistry. Recently, large metallo-organic complexes of ruthenium have been found to exhibit anti-tumor activity and the first of a new group of anti-cancer medicine are now in the stage of clinical trials. Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched in various, potential, solar energy technologies. HistoryRuthenium (Latin Ruthenia meaning "Russia") was discovered and isolated by Karl Klaus in 1844. Klaus showed that ruthenium oxide contained a new metal and obtained 6 grams of ruthenium from the part of crude platinum that is insoluble in aqua regia. Jöns Berzelius and Gottfried Osann nearly discovered ruthenium in 1827. The men examined residues that were left after dissolving crude platinum from the Ural Mountains in aqua regia. Berzelius did not find any unusual metals, but Osann thought he found three new metals and named one of them ruthenium. It is also possible that Polish chemist Jedrzej Sniadecki isolated element 44 (which he called vestium) from platinum ores in 1807. However his work was never confirmed and he later withdrew his discovery claim. OccurrenceThis element is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario and in pyroxinite deposits in South Africa. This metal is commercially isolated through a complex chemical process in which hydrogen is used to reduce ammonium ruthenium chloride yielding a powder. The powder is then consolidated by powder metallurgy techniques or by argon-arc welding. It is also possible to extract Ruthenium from burned-out nuclear fuel, which contains a few percent of Ruthenium. Ruthenium produced in such way contains radio active isotopes with times of half-life until 373.59 days and has therefore stored at least 30 years in a secured area, before it can be sold. CompoundsRuthenium compounds are often similar in properties to those of cadmium and exhibit at least eight oxidation states, but +2, +3, and +4 states are the most common. IsotopesNaturally occurring ruthenium is composed of seven isotopes. The most stable radioisotopes are Ru-106 with a half-life of 373.59 days, Ru-103 with a half-life of 39.26 days and Ru-97 with a half-life of 2.9 days. Fifteen other radioisotopes have been characterized with atomic weights ranging from 89.93 amu (Ru-90) to 114.928 (Ru-115). Most of these have half-lifes that are less than five minutes except Ru-95 (half-life: 1.643 hours) and Ru-105 (half-life: 4.44 h). The primary decay mode before the most abundant isotope, Ru-102, is electron capture and the primary mode after is beta emission. The primary decay product before Ru-102 is technetium and the primary mode after is rhodium. PrecautionsThe compound ruthenium tetroxide RuO4, similar to osmium tetroxide, is highly toxic and may explode. Ruthenium plays no biological role but does strongly stain human skin, may be carcinogenic and bio-accumulates in bone. References
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