Iridium (Ir)
Iridium (Ir) is element 77, a transition metal. Atomic mass 192.217, configuration [Xe] 4f¹⁴ 5d⁷ 6s². Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 77 |
|---|---|
| Symbol | Ir |
| Standard atomic weight | 192.217(2) |
| Category | Transition Metal |
| Group | 9 |
| Period | 6 |
| State at room temperature | Solid |
| Electron configuration | [Xe] 4f¹⁴ 5d⁷ 6s² |
| Valence electrons | 2 (Variable) |
| Common oxidation states | +3, +4 |
| Common ions | No common ions |
| Electronegativity (Pauling) | 2.2 |
| First ionization energy | 880 kJ/mol |
| Electron affinity | 150.9 kJ/mol |
| Atomic radius | 135 pm |
| Density | 22.56 g/cm³ |
| Melting point | 2446°C |
| Boiling point | 4428°C |
| Specific heat | 0.131 J/(g·°C) |
Natural isotopes
- Ir-191: Stable
- Ir-193: Stable
Common uses
- Spark plugs
- Crucibles
- Standard Metre Bar (Pt-Ir alloy)
Where it matters
- Geology (K-Pg boundary layer evidence for Dinosaur extinction)
Hazards
- Low toxicity
- dust is flammable
History
| Discovered | 1803 |
|---|---|
| Discovered by | Smithson Tennant |
| Name | From Greek iris (rainbow, due to salt colors) |