Ruthenium · element 44
The rare metal named for Russia that stores data on hard drives, hardens pen nibs and won a Nobel Prize for catalysis
Key facts
Ruthenium is the least famous of the platinum metals and one of the rarest elements in the crust, yet it is inside almost every hard disk drive made in the past two decades. A layer a few atoms thick beneath the magnetic film controls how the recording grains grow, part of what let disk capacities keep doubling.
It is a hard, brittle, silvery-white transition metal in group 8, beneath iron and above osmium. It resists acids, even the aqua regia that dissolves gold, and adopts more oxidation states than almost any other element, from minus two to plus eight. That flexibility makes it a gifted catalyst for making chlorine, ammonia, medicines and plastics.
Where it is found
Ruthenium occurs only alongside the other platinum group metals, in ores where all six are present in tiny concentrations. South Africa's Bushveld Complex supplies most of it, with Norilsk in Siberia, Sudbury in Canada and Stillwater in Montana as other sources. World production is only a few dozen tonnes a year.
Its crustal abundance is around one part per billion, comparable to or lower than gold. It occurs in the rare mineral laurite and in natural alloys with osmium and iridium, but is only ever recovered from the residues left after platinum, palladium and nickel have been extracted.
How it was discovered
Platinum from the Ural Mountains reached Russian laboratories in the 1820s, and in 1828 Gottfried Osann claimed three new metals in the insoluble residues, naming one ruthenium after Ruthenia, the Latin name for the lands of the Rus. His results could not be repeated.
In 1844 Karl Ernst Claus, a professor at Kazan University, worked through residues from the platinum refinery of the St Petersburg mint and isolated about six grams of a genuinely new metal. He kept Osann's name and sent samples to Berzelius, who confirmed the discovery. Ruthenium was the last of the six platinum metals to be found.
What we use it for
Electronics has been the largest market. Besides hard drive films, ruthenium oxide is the resistive material printed onto the chip resistors in every circuit board, and ruthenium is being adopted as wiring in the most advanced microchips because it conducts well when extremely thin. Titanium anodes coated with ruthenium oxide produce most of the world's chlorine and sodium hydroxide, and the same oxide stores charge in supercapacitors.
Ruthenium complexes developed by Robert Grubbs stitch carbon chains together in the metathesis reaction that earned the 2005 Nobel Prize in Chemistry and makes drugs and polymers. Other ruthenium catalysts make ammonia and liquid fuels. A small addition hardens platinum and palladium for jewellery, electrical contacts and fountain pen nibs, and a trace in titanium sharply improves its corrosion resistance. Ruthenium dyes powered the first efficient dye-sensitised solar cells, and ruthenium-106 plaques stitched onto the eye treat tumours.
Reading the numbers
Ruthenium melts at about 2334 °C and boils at 4150 °C, and it is so hard and brittle that it is shaped by pressing and heating powder rather than casting. Its density of 12.45 grams per cubic centimetre is greater than lead, though only a little over half that of platinum, so it is a heavy metal without being an extreme one.
The configuration [Kr] 4d7 5s1 places eight electrons outside the krypton core, the same total as iron above it, though iron keeps two s electrons. Those eight electrons can be shared out in many ways, which is why ruthenium ranges from the +2 and +3 states of its catalysts to the +8 of ruthenium tetroxide. The three measured ionisation energies, 710, 1620 and 2747 kJ/mol, are typical of a mid-period transition metal. Its electronegativity of 2.2 is high for a metal and marks it as noble: reluctant to give up electrons and therefore resistant to acids. Its place in group 8 explains the family resemblance to osmium, which shares the +8 state and the volatile, dangerous tetroxide.
Safety and the environment
Bulk ruthenium is inert and poses little hazard. Ruthenium tetroxide is another matter: it is volatile, a violent oxidiser and toxic to breathe, and it can react explosively with organic material, so it is handled only in small amounts. Some soluble ruthenium salts stain skin and are treated as potential irritants, though data on long-term effects are sparse.
Ruthenium-106 is a fission product with a one-year half-life. In 2017 a cloud of it drifted across Europe from an unannounced source, an episode never fully explained. Mining platinum metals is energy and water intensive, so recycling from electronics and spent catalysts matters for so scarce an element.
Did you know?
- Most hard disk drives made since the mid-2000s contain a ruthenium layer just a few atoms thick beneath the magnetic recording film.
- Ruthenium is one of the very few elements that can reach the +8 oxidation state, alongside osmium and xenon.
- The anodes that produce most of the world's chlorine are coated with ruthenium oxide.
- The 2005 Nobel Prize in Chemistry recognised ruthenium-based catalysts that let chemists snip and rejoin carbon chains.
- Ruthenium was the last of the six platinum group metals to be discovered, in 1844 at Kazan University.
- Small radioactive plaques of ruthenium-106 are sewn onto the surface of the eye to treat tumours and removed a few days later.
More in the transition metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 38 transition metals on one page, or browse all 118 elements.
Frequently asked questions
Is ruthenium a precious metal?
Yes. Ruthenium is one of the six platinum group metals and is traded as a precious metal, though it is usually far cheaper than platinum, rhodium or gold because industrial demand is smaller. Its price is volatile because supply depends on a handful of mines and it is produced only as a by-product.
Is ruthenium rarer than gold?
In the Earth's crust ruthenium is at least as scarce as gold, and many estimates put it lower, at around one part per billion. Annual production is only a few dozen tonnes compared with thousands of tonnes of gold. It seems less exotic only because it is not used for jewellery on its own.
What is ruthenium used for in jewellery?
Ruthenium is added in small amounts to platinum and palladium alloys to make them harder and more wear resistant, and it is electroplated onto white gold, silver and watch cases to give a dark grey or black finish. It also tips high-quality fountain pen nibs so they do not wear down.
Is ruthenium toxic?
The metal itself is inert and not considered toxic. Ruthenium tetroxide is highly toxic, volatile and a fire hazard, and some soluble ruthenium compounds can irritate skin and eyes. In everyday products such as electronics and jewellery, ruthenium is locked in a stable form and presents no risk.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Ruthenium reference article. Spotted an error? Tell us.