Ruthenium (Ru)
Element 44 · Transition metal · atomic mass 101.07 u · group 8, period 5
Electron shells: 2, 8, 18, 15, 1
Ruthenium is a hard platinum-group metal used in vanishingly thin layers where wear resistance matters. It is a superb catalyst, including for ammonia synthesis.
A layer just a few atoms thick helps hard drives pack more data onto each platter.
- Atomic number
- 44
- Atomic mass
- 101.07 u
- Electron configuration
- [Kr] 5s¹ 4d⁷
- Group · period · block
- 8 · 5 · d
- Oxidation states
- +3, +4
- Electronegativity
- 2.2 (Pauling)
- Melting point
- 2,334 °C
- Boiling point
- 4,150 °C
- Density
- 12.1 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-white, hard metal
- Discovered
- Karl Ernst Claus, 1827
44 protons, and 44 electrons when neutral
IUPAC standard atomic weight
Iron group
What Ruthenium is used for
- Wear-resistant electrical contacts
- Hard-disk platter coatings
- Chemical catalysts
- Fountain-pen nib tips
Atomic structure of Ruthenium
A neutral ruthenium atom has 44 protons and 44 electrons. Its most common isotope carries about 57 neutrons, which is where the mass number 101 comes from. Change the neutron count and you have a different isotope of ruthenium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 15, 1. In orbital notation that is [Kr] 5s¹ 4d⁷. As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Ruthenium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Ruthenium sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Iron — same group, so similar chemistry with a smaller atom.
- Directly below: Osmium — same group, one shell larger.
- One proton lighter: Technetium.
- One proton heavier: Rhodium.
Discovery and naming
Ruthenium was discovered by Karl Ernst Claus in 1827. Its name comes from Latin Ruthenia, "Russia".
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Ruthenium?
The standard atomic weight of Ruthenium is 101.07 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Ruthenium have?
Ruthenium has 44 protons, because the atomic number is the proton count and that is what makes an atom Ruthenium at all. A neutral Ruthenium atom has the same number of electrons, 44. The neutron count varies by isotope; the most common one has about 57, since 101 − 44 = 57.
What is the electron configuration of Ruthenium?
The electron configuration of Ruthenium is [Kr] 5s¹ 4d⁷. Its electrons are arranged 2, 8, 18, 15, 1 across 5 shells.
Is Ruthenium a metal?
Yes. Ruthenium is classified as a transition metal, on the metallic side of the table.
What group and period is Ruthenium in?
Ruthenium is in group 8 (the iron group), period 5, in the d-block. The group is its column and the period is its row.
What is the charge of Ruthenium?
Ruthenium most commonly forms a 3+ or 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Ruthenium?
Ruthenium melts at 2,334 °C and boils at 4,150 °C. That puts it in the solids at everyday temperatures.
What is Ruthenium used for?
Wear-resistant electrical contacts, Hard-disk platter coatings, Chemical catalysts, Fountain-pen nib tips. Ruthenium is a hard platinum-group metal used in vanishingly thin layers where wear resistance matters.
Who discovered Ruthenium, and where does its name come from?
Ruthenium (Ru) was discovered by Karl Ernst Claus in 1827. The name comes from Latin Ruthenia, "Russia".