Rhodium

Rhodium (Rh)

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.