Science, Tech, Math › Science Iridium Facts Chemical & Physical Properties of Iridium Share Flipboard Email Print Sztyopa / Wikimedia Commons / Public Domain Science Chemistry Periodic Table Basics Chemical Laws Molecules Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 10, 2020 Iridium has a melting point of 2410°C, a boiling point of 4130°C, a specific gravity of 22.42 (17°C), and valence of 3 or 4. A member of the platinum family, iridium is white like platinum, but with a slight yellowish cast. The metal is very hard and brittle and is the most corrosion-resistant metal known. Iridium is not attacked by acids or aqua regia, but it is attacked by molten salts, including NaCl and NaCN. Either iridium or osmium is the densest known element, but the data do not allow for selection between the two. Uses The metal is used for hardening platinum. It is used in crucibles and other applications requiring high temperatures. Iridium is combined with osmium to form an alloy used in compass bearings and for tipping pens. Iridium is also used for electrical contacts and in the jewelry industry. Sources of Iridium Iridium occurs in nature uncombined or with platinum and other related metals in alluvial deposits. It is recovered as a by-product of the nickel mining industry. Iridium Basic Facts Atomic Number: 77Symbol: IrAtomic Weight: 192.22Discovery: S.Tenant, A.F.Fourcory, L.N.Vauquelin, H.V.Collet-Descoltils 1803/1804 (England/France)Electron Configuration: [Xe] 6s2 4f14 5d7Word Origin: Latin iris rainbow, because the salts of iridium are highly coloredElement Classification: Transition Metal Iridium Physical Data Density (g/cc): 22.42Melting Point (K): 2683Boiling Point (K): 4403Appearance: white, brittle metalAtomic Radius (pm): 136Atomic Volume (cc/mol): 8.54Covalent Radius (pm): 127Ionic Radius: 68 (+4e)Specific Heat (@20°C J/g mol): 0.133Fusion Heat (kJ/mol): 27.61Evaporation Heat (kJ/mol): 604Debye Temperature (K): 430.00Pauling Negativity Number: 2.20First Ionizing Energy (kJ/mol): 868.1Oxidation States: 6, 4, 3, 2, 1, 0, -1Lattice Structure: Face-Centered CubicLattice Constant (Å): 3.840 References Los Alamos National Laboratory (2001)Crescent Chemical Company (2001)Lange, Norbert A. Lange's Handbook of Chemistry. 1952.CRC Handbook of Chemistry & Physics. 18th Ed.