ruthenium

Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a hard, silvery-white transition metal that belongs to the platinum group of the periodic table. In nature it occurs with other platinum-group metals in some ore deposits and is refined as a byproduct of mining for those metals.

Physically, ruthenium has a high melting point (about 2334°C) and a density around 12.4 g/cm3. It is resistant to corrosion and tarnish but can be brittle in certain forms. Ruthenium forms several oxides and a wide range of fluorides and chlorides. Isotopically, natural ruthenium comprises several stable isotopes; several radioactive isotopes exist.

It was discovered in 1844 by Karl Ernst Claus while processing platinum ore from the Ural Mountains. He named the element Ruthenium from Ruthenia, the Latin name for Rus’ (Russia).

Ruthenium is often used as an alloying agent to harden platinum and palladium alloys, improving strength and high-temperature stability. It is also employed in electrical contacts and as a coating for corrosion resistance. Ruthenium dioxide (RuO2) is a conductive oxide used in thick-film resistors and electrochemical sensors. Ruthenium catalysts are used in several industrial processes, including some oxidation and hydrogenation reactions. In dye-sensitized solar cells, ruthenium complexes act as light-absorbing dyes. Some ruthenium compounds are used in jewelry plating to provide a white, durable finish.

Like other heavy metals, ruthenium compounds can be toxic if ingested or inhaled; handling requires appropriate controls. The element is relatively rare and is primarily obtained as a byproduct of mining PGMs.