ElementsWhat is osmium?
Osmium is a hard, bluish-white metal of the platinum group. It is the densest of all natural elements.
What is osmium used for?
Very hard alloys for fountain pen tips, electrical contacts and instrument pivots.
Where the name comes from
From the Greek word osme, smell, for the sharp smell of its oxide.
Key facts
- Symbol
- Os
- Atomic number
- 76
- Atomic mass
- 190.2 u
- Family
- Transition metal
- Period
- 6
- Group
- 8
- Block
- d
- State at room temperature
- Solid
- Melting point
- 3,033 °C (3,306 K, 5,491 °F)
- Boiling point
- 5,012 °C (5,285 K, 9,053 °F)
- Density
- 22.57 g/cm³
- Electrons per shell
- 2, 8, 18, 32, 14, 2
- Electron configuration
- [Xe]6s2 4f14 5d6
- Common oxidation states
- +4, +3
- Electronegativity (Pauling)
- 2.2
- First ionisation energy
- 8.7 eV
- Electron affinity
- 1.1 eV
- Atomic radius (van der Waals)
- 216 pm
- Discovered
- 1803
Place in the periodic table
Osmium is element number 76. It sits in period 6 (row 6) of the periodic table, in group 8 (column 8), and belongs to the d-block. Just before it comes rhenium (75), and just after it comes iridium (77). In the same column, ruthenium is above it and hassium is below it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature osmium is a solid. It melts at 3,033 °C and boils at 5,012 °C, so it stays liquid over a range of 1,979 degrees. Its density is 22.57 grams per cubic centimetre, so a one-litre block would weigh about 22.57 kilograms. It is the densest element with a measured value. It has the 4th highest melting point of all elements.
Inside the atom
An atom of osmium has 76 protons in its nucleus and, when neutral, 76 electrons around it. The electrons are arranged in 6 shells: 2, 8, 18, 32, 14, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Xe]6s2 4f14 5d6.
Its electronegativity on the Pauling scale is 2.2. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 8.7 electronvolts (about 839 kilojoules per mole). One mole of osmium weighs 190.2 grams, so a single gram contains about 3.17 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains osmium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.