Rhodium

Rhodium (Rh)

Chemical Properties of Rhodium

Group 9 Melting point 1963°C, 3565°F, 2236 K

Period 5 Boiling point 3695°C, 6683°F, 3968 K

Block d Density (g cm−3) 12.4

Atomic number 45 Relative atomic mass 102.906

State at 20°C Solid Key isotopes ¹⁰³Rh,

Electron configuration [Kr] 4d⁸5s¹ CAS number 7440-16-6

ChemSpider ID 22389 ChemSpider is a free chemical database

Rhodium is one of the rarest elements, occurring in only one part of 109 in the earth’s crust. It has not been studied extensively and the interpretation of many of the published results are questionable due to uncertainties of the complex species involved. In general, rhodium chemistry resembles that of cobalt and to an even greater extent that of iridium.
As per the mineralogy of rhodium, only a little information has been collected. The minerals carry some rhodium in rare specimens and its content reaches 5 percent. Sperrylite may contain up to 0.72 percent of rhodium. Its metallic form is not soluble in aqua regia unless alloyed with gold, copper, lead, bismuth or platinum.
Its metallic form is harder, tougher and has a higher melting point than that of platinum or palladium. It is softer, more ductile and less brittle than metallic iridium.
Rhodium has a lower specific resistance and stable contact resistance due to the absence of oxide films on its surface. Metallic form of the element behaves more like platinum than palladium with respect to hydrogen. Compact rhodium absorbs very little H₂, while finely divided rhodium absorbs H2 readily. Compact rhodium is quite resistant to chemicals and attack by acids, even by aqua regia. Alkaline fusion is the usual technique for oxidizing the metal.

The extraction of this element is an intricate process because the ores mixed with other metals such as silver, platinum, gold, and palladium are rhodium-bearing minerals but are few in number. It is found in platinum ores and extracted as a white inert metal that is difficult to use.
Rhodium is primarily used in the production of platinum alloys, with resulting resistance materials and high hardness. These alloys are used in turbine reactors, electric ovens, glass industries and in catalytic nets for different chemical reactions.
The metal is also used in jewelry coating for silver objects and also circuit components, etc. Rhodium is an excellent coating for white gold jewels by the process of electrolytic deposition. This process makes the jewels more resistant and whiter.