Os
Osmium
Element 76 · Transition metal
Osmium (Os)
Osmium is a hard, brittle, bluish-white platinum-group metal and the densest naturally occurring element.
- Transition metal
- Period 6
- Group 8
- d-block
- solid at room temperature
Key properties
- Atomic mass
- 190.2
- u
- Electron configuration
- [Xe] 4f14 5d6 6s2
- Melting point
- 3,032.9 °C
- 3,306 K
- Boiling point
- 5,011.9 °C
- 5,285 K
- Density
- 22.57 g/cm³
- Electronegativity
- 2.2
- Pauling
- Atomic radius
- 216 pm
- van der Waals
- 1st ionisation energy
- 8.7 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about osmium
- 01
A brick of osmium the size of a milk carton would weigh about 22 kg.
- 02
Osmium tetroxide is highly toxic and is used to stain tissue for electron microscopes.
- 03
Osmium alloys were used in fountain-pen nibs and phonograph needles.
Applications
What is osmium used for?
- Hard alloy tips (pen nibs, contacts)
- Microscopy stains
- Catalysts
- Instrument pivots
History
Discovery & name origin
Discovered by
Year
Where
England
Name origin
Greek osme, “smell” — its oxide has a pungent odour.
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 76
- Atomic mass
- 190.2 u
- Group
- 8
- Period
- 6
- Block
- d-block
- Electron configuration
- [Xe] 4f14 5d6 6s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d6
- Electrons per shell
- 2, 8, 18, 32, 14, 2
- Electronegativity (Pauling)
- 2.2
- Electron affinity
- 1.1 eV
- Atomic radius (van der Waals)
- 216 pm
- Stable isotopes
- 6
Oxidation states
Highlighted: common oxidation states (+4, +3).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st840
- 2nd1,600
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 3,306 K · 3,032.9 °C · 5,491.1 °F
- Boiling point
- 5,285 K · 5,011.9 °C · 9,053.3 °F
- Density
- 22.57 g/cm³
- Molar heat capacity
- 24.7 J/(mol·K)
- Appearance
- Silvery, blue cast
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Osmium questions
What is Os on the periodic table?
Os is the symbol for osmium, element 76 on the periodic table. It sits in group 8, period 6, in the transition metal category, and has an atomic mass of 190.2.
What is the atomic number of osmium?
Osmium has atomic number 76, so every osmium atom has 76 protons in its nucleus. Its symbol is Os and its atomic mass is 190.2.
Who discovered osmium?
Osmium was discovered by Smithson Tennant in 1803 (England). The name comes from Greek osme, “smell” — its oxide has a pungent odour.
What is osmium used for?
Osmium is used for: hard alloy tips (pen nibs, contacts); microscopy stains; catalysts; instrument pivots.
Is osmium a metal?
Yes. Osmium is a transition metal, one of the metallic elements.
What is the electron configuration of osmium?
The electron configuration of osmium is [Xe] 4f14 5d6 6s2. Its 76 electrons are arranged in shells as 2, 8, 18, 32, 14, 2.