Ruthenium
Atomic Data
| Atomic Number | 44 |
| Symbol | Ru |
| Atomic Weight | 101.07 u |
| Density (STP) | 12.45 g/cm³ |
| Melting Point | 2333.85 °C (2607 K) |
| Boiling Point | 4149.85 °C (4423 K) |
| Electronegativity | 2.2 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d7 5s1 |
| Oxidation States | +2, +3, +4, +6, +8 |
| Phase at STP | Solid |
| Category | Transition Metal |
| Period / Group | 5 / 8 |
| CAS Number | 7440-18-8 |
Electron Configuration
[Kr] 4d7 5s1
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 7 | 43 |
| O | 5 | 5s | 1 | 44 |
| Total | 44 | 44 | ||
Isotopes of Ruthenium
Ruthenium has seven naturally occurring stable isotopes. The most abundant is ¹⁰²Ru, comprising 31.55% of all naturally occurring Ruthenium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Ruthenium-96 | ⁹⁶Ru | 44 | 52 | 5.54 | Stable |
| Ruthenium-98 | ⁹⁸Ru | 44 | 54 | 1.87 | Stable |
| Ruthenium-99 | ⁹⁹Ru | 44 | 55 | 12.76 | Stable |
| Ruthenium-100 | ¹⁰⁰Ru | 44 | 56 | 12.6 | Stable |
| Ruthenium-101 | ¹⁰¹Ru | 44 | 57 | 17.06 | Stable |
| Ruthenium-102 | ¹⁰²Ru | 44 | 58 | 31.55 | Stable |
| Ruthenium-104 | ¹⁰⁴Ru | 44 | 60 | 18.62 | Stable |
Abundance & Occurrence
Ruthenium is present in Earth's crust at approximately 0.001 ppm by mass and at approximately 5 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Ruthenium tetroxide (RuO4): acute hazard: RuO4 is a highly volatile, toxic, and powerfully oxidising solid; inhalation of its vapour causes severe respiratory damage, and it can also penetrate skin; it is formed by oxidation of ruthenium compounds and must be avoided.
- Inhalation of dusts and fumes: Ruthenium metal dust and ruthenium compound dusts are respiratory irritants; as with other platinum group metals, chronic exposure data is limited but precaution is warranted.
- Ruthenium-106: medical radiation: Ru-106 (t½ = 374 days, beta emitter) is used in ophthalmic brachytherapy; medical handling requires dosimetry and shielded applicators.
- General precautions: Avoid generating RuO4 by preventing contact of ruthenium compounds with strong oxidisers; work in ventilated hoods and use appropriate respiratory protection when handling powders.
Ruthenium in the Real World
Real-World Uses
- Hard disk drive coatings: A thin ruthenium interlayer between magnetic recording layers in perpendicular magnetic recording hard drives provides antiferromagnetic coupling that enables higher data storage densities.
- Catalysis: Ruthenium catalysts drive the ammonia synthesis reaction (an alternative to iron-based catalysts) and are used in the production of acetic acid, olefin metathesis reactions, and fuel cell electrodes.
- Dye-sensitised solar cells: Ruthenium polypyridyl complexes (N3, N719 dyes) are the light-absorbing dyes in Grätzel-type dye-sensitised solar cells (DSSCs), converting visible light to electricity in research and niche commercial applications.
- Jewellery and platinum alloying: Ruthenium is added to platinum and palladium jewellery alloys to increase hardness and durability; it also provides a dark electroplated finish used in watchcases and luxury pens.
- Chip resistors: Ruthenium oxide (RuO₂) thick-film pastes are fired onto ceramic substrates to form precision resistors in surface-mount electronic components used in all consumer and industrial electronics.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is ruthenium used for?
Ruthenium is used in electrical contacts and resistors (ruthenium oxide thick-film resistors are common in electronics), as a hardening agent in platinum and palladium alloys for jewellery and electrical contacts, and in catalysis. Ruthenium-based catalysts are used in ammonia synthesis and hydrocarbon processing. Ruthenium complexes, particularly tris(bipyridine)ruthenium, are intensively studied for dye-sensitised solar cells and photocatalysis.
Is ruthenium toxic?
Some ruthenium compounds are toxic and potentially carcinogenic: ruthenium tetroxide in particular is highly toxic and a strong oxidant. Elemental ruthenium and most of its common compounds have low to moderate toxicity. Ruthenium compounds can stain skin, and some cause irritation. As a platinum-group metal, occupational exposure should be minimised as a precaution.
How was ruthenium discovered?
Ruthenium was discovered in 1844 by Estonian-Russian chemist Karl Ernst Claus at the University of Kazan. He isolated it from platinum ores obtained from the Ural Mountains and named it ruthenium after Ruthenia, the Latin name for the historical region of Russia and Ukraine. It was the last of the platinum-group metals to be discovered.
What is the Grubbs catalyst and why does it involve ruthenium?
The Grubbs catalyst is a family of ruthenium-based organometallic compounds used for olefin metathesis: a reaction that rearranges carbon-carbon double bonds, allowing chemists to build complex organic molecules efficiently. Ruthenium is ideal for this role because its carbene complexes are stable in air and moisture, unlike earlier molybdenum and tungsten catalysts. The discovery of the Grubbs catalyst earned Robert Grubbs the 2005 Nobel Prize in Chemistry.