Ruthenium (Ru): Electron Configuration, Properties and Uses
Ruthenium (Ru): Electron Configuration, Properties and Uses
Electron configuration [Kr] 5s1 4d7 · group 8 · period 5 · Ar 101.07
Ruthenium data
- Atomic number
- 44
- Relative atomic mass
- 101.07
- Group
- 8
- Period
- 5
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Kr] 5s1 4d7
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7
- Electrons per shell
- 2, 8, 18, 15, 1 (K L M N O)
- Valence electrons
- 8
- Electronegativity (Pauling)
- 2.2
- First ionisation energy
- 7.361 eV
- Atomic radius (van der Waals)
- 207 pm
- State at room temperature
- Solid
- Melting point
- 2334 °C
- Boiling point
- 4150 °C
- Density
- 12.1 g/cm³
- Common oxidation states
- +3
- Discovered
- 1827
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 15 · O 1
Orbital diagram (outer electrons)
About ruthenium
Ruthenium, symbol Ru, is element number 44 in the periodic table. It is a transition metal in group 8, period 5, d-block. Ruthenium was first discovered in 1827. Ruthenium is a solid at room temperature, melting at 2334 °C and boiling at 4150 °C.
Ruthenium electron configuration
The electron configuration of ruthenium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7, or in short [Kr] 5s1 4d7. Its electrons occupy 5 shells: K = 2, L = 8, M = 18, N = 15, O = 1. For transition metals, valence electrons are counted from the 5s and 4d subshells: 1 + 7 = 8, matching group 8. This is an exception to the Aufbau rule: the usual filling order predicts [Kr] 5s2 4d6, but the 5s and 4d subshells are so close in energy that electrons occupy 4d. When it forms cations, electrons leave the outermost subshell first: Ru3+ = [Kr] 4d5.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s1(37) → 4d7(44)
Uses of ruthenium
Well-known applications of ruthenium include wear-resistant electrical contacts, catalysts (for example Grubbs metathesis catalysts), hard-disk media and dye-sensitised solar cells. For research and analysis you can browse ruthenium compounds in the AMI Scientific catalogue.
Safety
Ruthenium metal is generally safe to handle, but avoid breathing its dust and read the SDS before using Ruthenium compounds. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 8
Frequently asked questions
What is the electron configuration of ruthenium?
The electron configuration of ruthenium (Ru, atomic number 44) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d7, or [Kr] 5s1 4d7 in short. By shell: 2, 8, 18, 15, 1.
How many valence electrons does ruthenium have?
Ruthenium has 8 valence electrons.
Which group and period is ruthenium in?
Ruthenium is in group 8, period 5, d-block.
What is the atomic mass of ruthenium?
The relative atomic mass of ruthenium is 101.07. Use it to calculate molar mass with the molar mass calculator.
Need ruthenium compounds for your lab?
AMI Scientific is one of the official TCI distributors in Indonesia. Reagents with lot CoA & SDS, formal quotations and tax invoices for universities and laboratories.
Other formulas & calculators: molarity, mole, molality, normality, dilution, titration, pH, buffer, molar mass, ppm, mole fraction, mass percent, periodic table, chemical MSDS.
