Ruthenium

Karl Klaus extracted ruthenium in 1844 from the residues left after platinum refining in Kazan, and named it after Ruthenia, the Latin name for Rus. It is one of the rarest elements in the crust, at roughly 1 part per billion, and almost all of it is recovered as a by-product of platinum and nickel mining. Small additions harden platinum and palladium for electrical contacts and jewellery; thin ruthenium films are used as a barrier and adhesion layer in chip interconnects and in hard-disk platters. Its catalytic chemistry is where it earns its keep: ruthenium catalyses ammonia synthesis at lower pressures than iron, and Robert Grubbs built ruthenium carbene catalysts that made olefin metathesis a routine benchtop reaction, sharing the 2001 Nobel Prize. Ruthenium's ground state is the anomalous 4d⁷ 5s¹.