ElementsWhat is ruthenium?
Ruthenium is a hard, white, rare metal of the platinum group. It does not tarnish at room temperature.
What is ruthenium used for?
Hardening platinum and palladium for electrical contacts, coatings on computer hard disks, and catalysts.
Where the name comes from
From Ruthenia, a Latin name for Russia.
Key facts
- Symbol
- Ru
- Atomic number
- 44
- Atomic mass
- 101.1 u
- Family
- Transition metal
- Period
- 5
- Group
- 8
- Block
- d
- State at room temperature
- Solid
- Melting point
- 2,334 °C (2,607 K, 4,233 °F)
- Boiling point
- 4,150 °C (4,423 K, 7,502 °F)
- Density
- 12.1 g/cm³
- Electrons per shell
- 2, 8, 18, 15, 1
- Electron configuration
- [Kr]5s1 4d7
- Common oxidation states
- +3
- Electronegativity (Pauling)
- 2.2
- First ionisation energy
- 7.361 eV
- Electron affinity
- 1.05 eV
- Atomic radius (van der Waals)
- 207 pm
- Discovered
- 1827
Place in the periodic table
Ruthenium is element number 44. It sits in period 5 (row 5) of the periodic table, in group 8 (column 8), and belongs to the d-block. Just before it comes technetium (43), and just after it comes rhodium (45). In the same column, iron is above it and osmium is below it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature ruthenium is a solid. It melts at 2,334 °C and boils at 4,150 °C, so it stays liquid over a range of 1,816 degrees. Its density is 12.1 grams per cubic centimetre, so a one-litre block would weigh about 12.1 kilograms. By density it ranks 18th among the 96 elements with a measured value. It has the 9th highest melting point of all elements.
Inside the atom
An atom of ruthenium has 44 protons in its nucleus and, when neutral, 44 electrons around it. The electrons are arranged in 5 shells: 2, 8, 18, 15, 1. The outermost shell holds 1 electron. Written in full, the electron configuration is [Kr]5s1 4d7.
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 7.361 electronvolts (about 710 kilojoules per mole). One mole of ruthenium weighs 101.1 grams, so a single gram contains about 5.96 × 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 ruthenium 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.