Rhodium is one of the of the six platinum group metals: platinum, palladium, rhodium, osmium, iridium and ruthenium. It is also classified as a noble metal, meaning that it does not react to oxygen easily, acts as a fantastic catalyst and is resistant to corrosion and oxidation. Some common characteristics of the platinum group metals include high melting points, general non-toxicity, and resistance to wear, oxidation and corrosion, according to Chemistry Libretexts.
Rhodium is the rarest of the platinum group, only occurring up to one part per 200 million in the Earth’s crust, according to Chemistry Libretexts. Rhodium has lower density and a higher melting point than platinum. Rhodium it is unaffected by air and water up to 1,112 degrees Fahrenheit (600 degrees Celsius), according to Lenntech.Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope: ¹⁰³Rh.