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iridium (Ir)





iridium powder
High-purity iridium powder.
Image copyright: smart-elements.com

A very hard and brittle, exceptionally corrosion-resistant, silvery-white metallic element. Iridium is a transition element and a member of the platinum group. It occurs in platinum ore and is used principally to harden platinum and in high-temperature materials, surgical and scientific instruments, electrical contacts, pen tips, and and wear-resistant bearings. It is also used to encapsulate radioactive fuels on spacecraft. Discovered by Smithson Tennant in London in 1803, its name comes from the Latin iris (stem irid-) for "rainbow," from the variety of colors in gives in solution. Its most common isotope is 193Ir (62.6%).


atomic number 77
relative atomic mass 192.2
relative density 22.42 (at 17°C)
melting point 2,140°C
boiling point 4,527°C


Related category

   • INORGANIC CHEMISTRY