About

Iridium is a very hard, brittle, silvery-white metal from the platinum group. It is considered the most corrosion-resistant metal known, withstanding attack from nearly all acids, aqua regia, and high temperatures. It is used in high-performance spark plugs, crucibles for growing industrial crystals, and its abundance in a geological layer is evidence for the asteroid impact that wiped out the dinosaurs.

Atomic Properties

Atomic Number77

Atomic Weight192.217 u

Neutrons (common)116

Electron Configuration[Xe] 4f¹⁴ 5d⁷ 6s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d⁷ 6s²

Electrons per Shell2, 8, 18, 32, 15, 2

Electronegativity2.2

Electron Affinity150.94 kJ/mol

Oxidation States-3, -1, 0, +1, +2, +3, +4, +5, +6

Covalent Radius135 pm

Ionic Radius68 pm

Periodic Table Position

Group9

Period6

BlockD

Chemical SeriesTransition metals

Physical Properties

State at STPsolid

Appearancesilvery white

Crystal Structurefcc

Magnetic Orderingparamagnetic

Speed of Sound4,825 m/s

Poisson Ratio0.26

Thermal Properties

Melting Point2,719 K

Boiling Point4,701 K

Thermal Expansion0 1/K

Thermal Conductivity147 W/(m·K)

Specific Heat0.131 J/(g·K)

Molar Heat25.1 J/(mol·K)

Heat of Fusion41.12 kJ/mol

Heat of Vaporization604 kJ/mol

Abundance

In Earth's Crust0.001 ppm

In Solar System0.002 ppm

In Universe0.002 ppm

Discovery

Discovered bySmithson Tennant

Discovery Year1,803

Occurrenceprimordial

CAS Number7439-88-5

Electron Configuration

Energy

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Isotopes of Iridium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
¹⁹¹Ir	190.960590	37.3%	Stable	Stable
¹⁹³Ir	192.962920	62.7%	Stable	Stable

Interactive Visualization

Explore the 3D Bohr model of Iridium in our interactive viewer.

View 3D Model of Iridium