Rhodium melted pellet. Image copyright: smart-elements.com

Rhodium is a moderately hard, silvery-white, metallic element belonging to the platinum group of transition elements. It was discovered by William Wollaston in London in 1803; its name comes from the Greek rhodon meaning "rose." It is the rarest metal on Earth and occurs associated with platinum. Its chief source is a by-product of nickel smelting.


Rhodium resists tarnishing and corrosion; it is used in hard platinum alloys, as a mirror surface, to plate jewelry, and in an alloy with platinum as a catalyst in the Ostwald process. Its most common isotope is 103Rh (100%).


atomic number 45
relative atomic mass 102.91
electron configuration [Kr]4d8 5s1
relative density 12.4
melting point 1,966°C (3,571°F)
boiling point 3,727°C (6,741°F)