Ruthenium – facts and properties
- Symbol
- Ru
- Atomic number
- 44
- Atomic mass
- 101.07 u
- Period
- 5
- Group
- 8
- Category
- transition metal
- Electron configuration
- [Kr] 4d⁷ 5s¹
- Electronegativity
- 2.2
- Atomic radius
- 178 pm
- Valence electrons
- 8
- State at standard conditions
- solid
- Melting point
- 2334 °C
- Boiling point
- 4150 °C
- Density
- 12.1 g/cm³
- Discovered
- 1827
Ruthenium is a hard, silvery-white metal with atomic number 44 and belongs to the platinum metals. Its name comes from Ruthenia, the Latin name for Russia, because it was found in ore from the Urals. Ruthenium is very rare and corrosion-resistant. It is used in tiny layers in hard disks and electronics, as a hardener for other precious metals and above all as a catalyst in chemistry, where it helped earn two Nobel Prizes.
Position in the periodic table
Occurrence and extraction
Ruthenium is among the rarest stable elements in the Earth's crust. It occurs as a companion of other platinum metals, mostly in their natural alloys and in traces in nickel-copper sulfide ores. Important deposits lie in South Africa, as well as in Russia and North America. It is obtained as a by-product of platinum production, after platinum, palladium, gold and silver have been separated from the anode slime of nickel and copper refining. Only a few dozen tonnes are produced each year.
The discovery story is tangled. The chemist Gottfried Osann at Dorpat, today's Tartu, studied residues of Russian platinum and thought he had found new metals in them. The year of his report, 1827, is listed as the year of discovery in some tables. Osann's findings were not clean, however, and he had to withdraw them. Only in 1844 did the chemist Karl Ernst Claus at the University of Kazan prepare the element in purer form and confirm it. He kept the name that Osann had proposed and so recalled Russia.
In nuclear reactors the radioactive isotope ruthenium-106 also forms as a fission product, and it can be detectable after an accident or a release.
Properties and reactions
Ruthenium is in period 5 and group 8, below iron. Its electron configuration is [Kr] 4d⁷ 5s¹ and its electronegativity is 2.2. The metal has a density of 12.1 g/cm³, melts at 2334 °C and boils at 4150 °C. It is hard and brittle and difficult to shape.
Like the other precious metals, ruthenium reacts with difficulty. Acids hardly attack it, and even aqua regia does not dissolve it to any noticeable extent. Melts with alkali hydroxides and oxidising agents are effective, however. Striking is the range of oxidation numbers: they run from minus two to plus eight, and plus two, plus three and plus four are the most common. Many ruthenium compounds are coloured.
Ruthenium tetroxide, RuO₄, is the highest oxide. It is a yellow, volatile solid and a very strong oxidising agent that is toxic and reacts violently with organic matter. It has no place in school lessons. The dioxide RuO₂ is easier to handle, an electrically conducting substance used as a coating for electrodes.
The metal is an excellent catalyst. Its surface and its compounds speed up many reactions without being used up themselves.
Uses in everyday life and technology
Most of it goes into electronics. Thin ruthenium films a few atomic layers thick separate two magnetic layers in hard disks and couple them so that more data fits on the same area. Ruthenium is also found in resistor pastes for chips and in contacts. In metallurgy it acts as a hardener: a small addition makes platinum and palladium more durable, for instance for jewellery, pen nibs and electrical contacts.
Chemistry uses ruthenium chiefly as a catalyst. Olefin metathesis, in which carbon-carbon double bonds are broken and rejoined, runs especially mildly and flexibly with ruthenium catalysts. Robert Grubbs received the Nobel Prize in Chemistry for this in 2005, together with Yves Chauvin and Richard Schrock. It is used to make drugs, plastics and fine chemicals. Ruthenium is also behind the asymmetric hydrogenation of Ryōji Noyori, honoured with the Nobel Prize in 2001, which yields only one of the two mirror-image forms of a molecule.
Further uses are dyes for solar cells, which capture light, and processes for ammonia synthesis. In research, ruthenium compounds are also studied as possible anti-cancer agents.
Molecules containing this element
- Ruthenium neodecanoate Ru(C9H19COO)4
Quick question
What is the atomic number of ruthenium (Ru)?
FAQ
Why is ruthenium called ruthenium?
The name comes from Ruthenia, the medieval Latin name for Russia. The element was found in platinum ore from the Urals, and the chemist Claus, who worked in Kazan, confirmed it under this name.
What is ruthenium used for?
As a wafer-thin layer in hard disks, as a hardener for platinum and palladium and above all as a catalyst. Ruthenium catalysts enable olefin metathesis, which is used to make drugs and plastics.
What does ruthenium have to do with the Nobel Prize?
Robert Grubbs, Yves Chauvin and Richard Schrock received the 2005 Nobel Prize in Chemistry for metathesis. The well-known Grubbs catalysts contain ruthenium. Ryōji Noyori also used ruthenium and was honoured in 2001 for asymmetric hydrogenations.