Ruthenium or Ru Element Facts

Ruthenium Chemical & Physical Properties

This sample of ruthenium has been etched. Jurii/ Creative Commons License

Ruthenium or Ru is a hard, brittle, silvery-white transition metal that also belongs to the noble metals and platinum metals group in the periodic table. While it does not readily tarnish, the pure element can form a reactive oxide that can explode. Here are physical and chemical properties and other ruthenium facts:

Element Name: Ruthenium

Symbol: Ru

Atomic Number: 44

Atomic Weight: 101.07

Uses of Ruthenium

  • Ruthenium is one of the best hardeners for addition to palladium or platinum. It is alloyed with these metals to make electrical contacts with extreme wear resistance.
  • Ruthenium is used to plate other metals. Thermal decomposition or electrodeposition are the most common metals used to make ruthenium coatings.
  • One ruthenium-molybdenum alloy is superconductive at 10.6 K.
  • Adding 0.1% ruthenium to titanium improves its corrosion resistance by a factor of a hundred.
  • Ruthenium oxides are versatile catalysts.
  • Ruthenium is used in some pen nibs. (Don't chew on your pen!)

Interesting Ruthenium Facts

  • Ruthenium was the last of the platinum group metals to be discovered.
  • The element name comes from the Latin word ‘Ruthenia’. Ruthenia means Russia, which refers to the Ural Mountains of Russia, the original source of the platinum metal group ores.
  • Ruthenium compounds are similar to those formed by the element cadmium. Like cadmium, ruthenium is toxic to humans. It is believed to be a carcinogen. Ruthenium tetroxide (RuO4) is considered particularly dangerous.
  • Ruthenium compounds stain or discolor skin.
  • Ruthenium is the only group 8 element that does not have 2 electrons in its outer shell.
  • The pure element is susceptible to attack by halogens and hydroxides. It is not affected by acids, water, or air.
  • Karl K. Klaus was the first to isolate ruthenium as a pure element. This was an involved process in which he first prepared the salt, ammonium chlororuthenate, (NH4)2RuCl6, and then isolated the metal from it in order to characterize it.
  • Ruthenium displays a wide range of oxidation states (7 or 8), although it is most commonly found in the II, III, and IV states.
  • Pure ruthenium costs around $1400 per 100 grams of the metal.
  • The element abundance in the Earth's crust is estimated to be 1 part per billion by weight. The abundance in the solar system is believed to be about 5 parts per billion by weight.

Sources of Ruthenium

Ruthenium occurs with other members of the platinum group of metals in the Ural mountains and in North and South America. It is also found in the Sudbury, Ontario nickel-mining region and in the pyroxinite deposits of South Africa. Ruthenium may also be extracted from radioactive waste.

A complex process is used to isolate ruthenium. The final step is hydrogen reduction of ammonium ruthenium chloride to yields a powder that is consolidated by powder metallurgy or argon-arc welding.

Element Classification: Transition Metal

Discovery: Karl Klaus 1844 (Russia), however, Jöns Berzelius and Gottfried Osann discovered impure ruthenium in 1827 or 1828

Density (g/cc): 12.41

Melting Point (K): 2583

Boiling Point (K): 4173

Appearance: silvery-gray, extremely brittle metal

Atomic Radius (pm): 134

Atomic Volume (cc/mol): 8.3

Covalent Radius (pm): 125

Ionic Radius: 67 (+4e)

Specific Heat (@20°C J/g mol): 0.238

Fusion Heat (kJ/mol): (25.5)

Pauling Negativity Number: 2.2

First Ionizing Energy (kJ/mol): 710.3

Oxidation States: 8, 6, 4, 3, 2, 0, -2

Electron Configuration: [Kr] 4d7 5s1

Lattice Structure: Hexagonal

Lattice Constant (Å): 2.700

Lattice C/A Ratio: 1.584


  • Los Alamos National Laboratory (2001)
  • Crescent Chemical Company (2001)
  • Lange's Handbook of Chemistry (1952)
  • CRC Handbook of Chemistry & Physics (18th Ed.)