Quick Facts
| Property | Value |
|---|---|
| Symbol | Ir |
| Atomic Number | 77 |
| Atomic Mass | 192.22 u |
| Category | Transition Metal |
| Period | 6 |
| Group | 9 |
| Block | d |
| Electron Configuration | [Xe] 4f¹⁴ 5d⁷ 6s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 22.56 g/cm³ |
| Melting Point | 2466°C (2739 K) |
| Boiling Point | 4428°C (4701 K) |
| Appearance | Silvery-white, hard metal |
History and Discovery
Discovered by: Smithson Tennant Year of Discovery: 1803 Location: London, England
Etymology
Named after Iris, Greek goddess of the rainbow, because of its colorful compounds.
Applications and Uses
- Spark plugs
- Crucibles for crystal growing
- International prototype kilogram (historical)
- Fountain pen nibs
- Cancer treatment (Ir-192 brachytherapy)
Interesting Facts
- Second-densest element (very close to osmium)
- Most corrosion-resistant metal known
- K-T boundary iridium layer linked to dinosaur extinction asteroid
- The old kilogram standard was made of platinum-iridium
- Extremely rare on Earth but more common in meteorites