Osmium (Os)

Osmium properties

Atomic number

76

Atomic mass

190.23 u

Category

Transition metal

Group

8

Period

6

Block

d-block

State at room temp.

Solid

Electronegativity

2.2

Melting point

3,306 K (3,032.8 °C)

Boiling point

5,285 K (5,011.8 °C)

Density

22.59 g/cm³

Valence electrons

2

Common charges

+3, +4

Oxidation states

+4, +3

Atomic radius

216 pm

Ionization energy

8.7 eV

Electron affinity

1.1 eV

Radioactive

No, has stable isotopes

Discovered

1803

Osmium electron configuration

The electron configuration of Osmium (Os) is [Xe] 4f14 5d6 6s2. Its 76 electrons are arranged in shells as 2, 8, 18, 32, 14, 2.

Protons, neutrons and electrons in Osmium

A neutral Osmium atom has 76 protons and 76 electrons. Most Osmium atoms have about 114 neutrons: the atomic mass rounded to 190, minus the atomic number 76.

Neutrons are approximate: atoms of the same element can have different numbers of neutrons (isotopes). Atomic number and mass

How many valence electrons does Osmium have?

2

Osmium has 2 valence electrons, counting the electrons in its outermost s subshell. Like most transition metals, it can also use d electrons in bonding.

See every element: Periodic table with valence electrons

Osmium orbital diagram

Each box is an orbital that holds up to two electrons with opposite spins (↑↓). The inner shells are the same as the noble gas in brackets. How to write electron configurations

Molar mass of Osmium

190.23 g/mol

One mole of Osmium atoms (6.022 × 10²³ atoms) has a mass of 190.23 grams. Use this value to convert between grams and moles.

Osmium facts

• Osmium is the densest naturally occurring element, slightly denser than iridium.
• Its name comes from the Greek osme, meaning 'smell', because its volatile oxide has a sharp, chlorine-like odor.
• Osmium (Os) has atomic number 76 and is a solid at room temperature. It was discovered in 1803.

Position in the periodic table

Osmium is element 76, in period 6 and group 8 of the periodic table, in the d-block.

All transition metals

Uses of Osmium

Osmium is rare and its oxide is toxic, so it has few uses. Hard osmium alloys have been used for fountain pen tips, instrument pivots, and electrical contacts that must resist wear. Osmium tetroxide is used to stain fatty tissues for electron microscopy and as a catalyst in organic chemistry, and it has also been used to reveal fingerprints.

Who discovered Osmium?

English chemist Smithson Tennant discovered osmium in 1803 in London, in the black residue left after dissolving platinum ore in aqua regia; he found iridium in the same residue.

Where does the name come from?

Osmium comes from the Greek osme, meaning 'smell'. Smithson Tennant named it in 1803 because of the sharp, unpleasant smell of osmium tetroxide, a volatile compound that forms when the metal reacts with air.

Discovery timeline