About

Osmium is the densest naturally occurring element, twice as dense as lead. It is a hard, brittle, blue-white transition metal from the platinum group. Due to its extreme hardness and durability, it is used in alloys for high-wear applications like fountain pen tips, electrical contacts, and instrument pivots. Its oxide is highly toxic and has a sharp smell.

Atomic Properties

Atomic Number76

Atomic Weight190.23 u

Neutrons (common)116

Electron Configuration[Xe] 4f¹⁴ 5d⁶ 6s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d⁶ 6s²

Electrons per Shell2, 8, 18, 32, 14, 2

Electronegativity2.2

Electron Affinity103.99 kJ/mol

Oxidation States-2, 0, +2, +3, +4, +5, +6, +8

Covalent Radius144 pm

Ionic Radius63 pm

Periodic Table Position

Group8

Period6

BlockD

Chemical SeriesTransition metals

Physical Properties

State at STPsolid

Appearancesilvery, hard, brittle, blue-white

Crystal Structurehcp

Magnetic Orderingparamagnetic

Speed of Sound4,940 m/s

Poisson Ratio0.25

Thermal Properties

Melting Point3,306 K

Boiling Point5,285 K

Thermal Expansion0 1/K

Thermal Conductivity87.6 W/(m·K)

Specific Heat0.13 J/(g·K)

Molar Heat24.7 J/(mol·K)

Heat of Fusion57.85 kJ/mol

Heat of Vaporization738 kJ/mol

Abundance

In Earth's Crust0.002 ppm

In Solar System0.001 ppm

In Universe0.003 ppm

Discovery

Discovered bySmithson Tennant

Discovery Year1,803

Occurrenceprimordial

CAS Number7440-04-2

Electron Configuration

Energy

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Isotopes of Osmium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
¹⁸⁴Os	183.952490	0.02%	Stable	Stable
¹⁸⁶Os	185.953830	1.59%	2.0 Py	Alpha Decay
¹⁸⁷Os	186.955750	1.96%	Stable	Stable
¹⁸⁸Os	187.955840	13.24%	Stable	Stable
¹⁸⁹Os	188.958140	16.15%	Stable	Stable
¹⁹⁰Os	189.958440	26.26%	Stable	Stable
¹⁹²Os	191.961480	40.78%	Stable	Stable

Interactive Visualization

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

View 3D Model of Osmium