Iridium

Iridium (pronounced /ɨˈrɪdiəm/, i-RID-ee-əm) is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust... more

Iridium (pronounced /ɨˈrɪdiəm/, i-RID-ee-əm) is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can even be flammable. The most important iridium compounds in terms of use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in catalysis and in research. Ir and Ir are the only two naturally occurring isotopes of iridium as well as the only stable isotopes; the latter is the more abundant of the two. Iridium was discovered in 1803 by Smithson Tennant in London, England, among insoluble impurities in natural platinum from South America. Although it is... less