![Iridium element card: symbol Ir, atomic number 77, atomic mass 192.22, electron configuration [Xe] 4f¹⁴ 5d⁷ 6s², oxidation states +4 +3, Transition metal, group 9, period 6, solid at room temperature.](https://stage.chemistry-dictionary.com/wp-content/uploads/2026/09/iridium-chemical-element.webp)
Iridium sits in group 9 of the periodic table as a heavy transition metal. It is much more common in space rocks than in the outer crust of our planet. When the early Earth was hot and molten, heavy metals like iridium sank into the deep core.
Students often think iridium is rare everywhere, but it is actually abundant in Earth’s core. High levels of this metal in rock layers point to past asteroid impacts. One famous impact released enough iridium dust to cause the dinosaur extinction.
Iridium resists rust and decay much better than any other metal on Earth. No single acid can dissolve this stubborn metal at room temperature. Even a very strong acid mixture called aqua regia cannot dissolve solid iridium.
In chemical compounds, iridium mostly takes plus 3 and plus 4 oxidation states. An oxidation state shows how many electrons an atom shares or transfers. It can even reach a plus 9 state in the [IrO4]+ cation.
A cation is a positively charged ion that forms during chemical reactions. This rare cation represents the highest known oxidation state for any element. Miners extract iridium as a byproduct of nickel and copper mining.
They find it mixed inside sulfide ores alongside other metals like platinum. Its extreme hardness and brittle nature make it very difficult to shape. Workers must use special high-temperature methods to mold this metal.