76
Os
Osmium
192
Osmium (Os)
Transition MetalGroup 8Period 6d-block-block
Osmium (from Greek osme (ὀσμή) meaning "smell") is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with a density of 22.59 g/cm3.
Latin name: Osmium
Atomic Number
76
Atomic Mass
192 g/mol
Phase (STP)
Solid
Electron Config.
[Xe] 4f¹⁴ 5d⁶ 6s²
General
SymbolOs
Atomic Number76
Atomic Mass192 g/mol
CategoryTransition Metal
Group8
Period6
Blockd-block
Electron Configuration[Xe] 4f¹⁴ 5d⁶ 6s²
Valence Electrons8
Colourblue-gray metallic
Appearancesilvery, blue cast
CAS NumberCAS7440-04-2
Physical Properties
Phase (STP)Solid
Density22.59 g/cm³
Melting Point3032.85°C · 5491.13°F · 3306.00 K
Boiling Point5011.85°C · 9053.33°F · 5285.00 K
Atomic Properties
Atomic Radius216 pm
Electronegativity2.2 Pauling
Ionization Energy840 kJ/mol
Oxidation States+8, +6, +4, +3, +2
Ion ChargeOs2+/Os3+/Os4+/Os6+/Os8+
Thermodynamic
Molar Heat24.7 J/(mol·K)
Crystal Structure
Crystal Structurehexagonal close-packed
Mechanical Properties
Mohs Hardness7
Nuclear & Hazards
Half-lifestable
Abundance
In Universe0.000002%
In Sun0.0000018%
In Earth's Crust0.000002%
Discovery & History
Discovery Year1803
Discovered BySmithson Tennant
Country of DiscoveryEngland
Isotopes of Osmium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Os-184 | 0.02% | Stable | — |
| Os-186 | 1.59% | 2.0 × 10¹⁵ years | α |
| Os-187 | 1.96% | Stable | — |
| Os-188 | 13.24% | Stable | — |
| Os-189 | 16.15% | Stable | — |
| Os-190 | 26.26% | Stable | — |
| Os-192 | 40.93% | Stable | — |