Tukuk-OSIridium
Transition metal · atomic number 77
Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser. It is also 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 be flammable.
Properties of Iridium
| Element category | Transition metal |
|---|---|
| Atomic number | 77 |
| Atomic mass | 192.2173 u |
| Phase at STP | Solid |
| Group | 9 |
| Period | 6 |
| Block | d |
| Electron configuration | [Xe] 4f14 5d7 6s2 |
| Electrons per shell | 2, 8, 18, 32, 15, 2 |
| Electronegativity (Pauling) | 2.2 |
| Melting point | 2719 K (2446 °C) |
| Boiling point | 4403 K (4130 °C) |
| Density | 22.56 g/cm3 |
| Discovered by | Smithson Tennant |
← Osmium · Periodic table · Platinum → Pt
About the transition metal group
The dense, strong, catalytic heart of the table — iron, copper, gold, titanium — responsible for most of metallurgy, jewellery and industry.