Iridium (Ir)
Transition metal · d-block · period 6 · group 9
Hard, brittle, silvery-white, very dense metal with a slight yellow cast.
Iridium (symbol Ir) is chemical element number 77, a transition metal in group 9, period 6 of the periodic table. Its standard atomic weight is 192.22 and its electron configuration is [Xe] 4f14 5d7 6s2. At room temperature it is a solid. The most corrosion-resistant metal known — nothing attacks it below 2,000 °C.
Properties
| Atomic number | 77 |
|---|---|
| Atomic mass | 192.22 |
| Category | Transition metal |
| Block | d-block |
| Group · Period | 9 · 6 |
| Electron configuration | [Xe] 4f14 5d7 6s2 |
| Electrons per shell | 2, 8, 18, 32, 15, 2 |
| State at 25 °C | solid |
| Melting point | 2719 K |
| Boiling point | 4701 K |
| Density | 22.56 g/cm³ |
| Electronegativity (Pauling) | 2.2 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1803 · Smithson Tennant |
Key facts about Iridium
- The most corrosion-resistant metal known — nothing attacks it below 2,000 °C.
- A worldwide thin layer of iridium in the rocks is the fingerprint of the asteroid that killed the dinosaurs.
- The international standard kilogram was a platinum-iridium cylinder.
- Its name comes from Iris, the rainbow goddess, for its many-coloured salts.
What Iridium is used for
Spark-plug tips, crucibles for growing crystals, standard weights, deep-sea and spacecraft parts, catalysts.
Where it sits in the periodic table
Iridium is in group 9, period 6, of the d-block. Its electron configuration [Xe] 4f14 5d7 6s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Iridium on the interactive table →
Iridium — frequently asked questions
What is Iridium used for?
Spark-plug tips, crucibles for growing crystals, standard weights, deep-sea and spacecraft parts, catalysts.
Is Iridium radioactive?
No. Iridium has at least one stable isotope and is not radioactive.
What is the electron configuration of Iridium?
Iridium has the electron configuration [Xe] 4f14 5d7 6s2, which is 2, 8, 18, 32, 15, 2 electrons per shell.
What group and period is Iridium in?
Iridium is in group 9, period 6, in the d-block. Its outer shell holds 2 electrons.
Who discovered Iridium?
Iridium was discovered in 1803 by Smithson Tennant.