Ruthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys.
A polyvalent hard white metal, ruthenium is a member of the platinum group, has four crystal modifications and does not tarnish at normal temperatures, but does oxidize readily on exposure to air to form ruthenium tetroxide, RuO4, a strong oxidising agent with properties analogous to those of osmium tetroxide. Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by halogens at high temperatures. Small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is increased markedly by the addition of a small amount of ruthenium.
This metal can be plated either through electrodeposition or by thermal decomposition methods. One ruthenium-molybdenum alloy has been found to be superconductive at 10.6 K. The oxidation states of ruthenium range from +1 to +8, and -2 is known, though oxidation states of +2, +3, and +4 are most common.
||Melting point / °C
|No. of naturally occurring isotopes
||Boiling point / °C
|Ionic radius(4-coordinate)/pm VIII
|Ionic radius(4-coordinate)/pm VII
|Ionic radius(6-coordinate)/pm V
||Ionization energy/kJmol-1 I
|Ionic radius(6-coordinate)/pm IV
||Ionization energy/kJmol-1 II
|Ionic radius(6-coordinate)/pm III
||Ionization energy/kJmol-1 III
|Temperature (oC) @Vap. Pressure
||Spits violently in EB, requires degas.