Rhodium

Rhodium,  ₄₅Rh

General properties
Name, symbol	Rhodium, Rh
Appearance	Silvery white metal
Rhodium in the periodic table
Co ↑ Rh ↓ Ir Ruthenium ← Rhodium → Palladium
Atomic number	45
Standard atomic weight (Ar)	102.90550(2)
Group, block	9; d-block
Period	period 5
Electron configuration	[Kr] 4d8 5s1
per shell	2, 8, 18, 16, 1
Physical properties
Silvery-white
Phase	Solid
Melting point	2237 K ​(1964 °C, ​3567 °F)
Boiling point	3968 K ​(3695 °C, ​6683 °F)
Density near r.t.	12.41 g/cm3
when liquid, at	10.7 g/cm3
Heat of fusion	26.59 kJ/mol
Heat of	493 kJ/mol
Molar heat capacity	24.98 J/(mol·K)
pressure
Atomic properties
Oxidation states	6, 5, 4, 3, 2, 1, −1, −3 ​an amphoteric oxide
Electronegativity	Pauling scale: 2.28
energies	1st: 719.7 kJ/mol 2nd: 1740 kJ/mol 3rd: 2997 kJ/mol
Atomic radius	empirical: 134 pm
Covalent radius	142±7 pm
Miscellanea
Crystal structure	​face-centered cubic (fcc)
Speed of sound thin rod	4700 m/s (at 20 °C)
Thermal expansion	8.2 µm/(m·K) (at 25 °C)
Thermal conductivity	150 W/(m·K)
Electrical resistivity	43.3 Ω·m (at 0 °C)
Magnetic ordering	Paramagnetic
Young's modulus	380 GPa
Shear modulus	150 GPa
Bulk modulus	275 GPa
Poisson ratio	0.26
Mohs hardness	6.0
Vickers hardness	1100–8000 MPa
Brinell hardness	980–1350 MPa
CAS Registry Number	7440-16-6
Discovery and first isolation	William Hyde Wollaston (1804)

Rhodium is a chemical element, a silvery-white hard platinum group metal. It has the symbol Rh and atomic number 45.

Properties

Chemical

Rhodium is extremely resistant to corrosion. It is unaffected by most acids, even when hot. Aqua regia has negligible effect. Oxygen is absorbed from the atmosphere only at the melting point of rhodium, but is released on solidification.

Physical

Rhodium is a silvery white, hard, durable metal that has a high reflectance. It has a high melting point of 1964 °C and a boiling point of 3695 °C. It is a dense metal, with a value of 12.41 g/cm³.

Availability

Rhodium is sold by various chemical suppliers. It is also sometimes sold as jewels.

Rhodium is also found in many car catalytic converters, though the amount is small and it's an alloy with other platinum-group metals.

Isolation

As rhodium is extremely inert, rhodium can be isolated from its compounds with any reducing agent, however the amount obtained is low. It's best to simply buy the pure element.

Projects

• Electroplating
• Element collecting

Handling

Safety

Rhodium, like all platinum group metals is inert and plays no biological role. It is harmless.

However, chemical complexes of rhodium can be reactive and toxic.

Storage

Rhodium can be stored in any container.

Disposal

Due to the high price of rhodium and its rarity, it's best to recycle rhodium instead of throwing it away.

References

Relevant Sciencemadness threads

• Rhodium solution
• get RHODIUM out of glassware
• Rhodium plating?
• Rhodium Analysis