Rhodium

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Rhodium,  45Rh
General properties
Name, symbol Rhodium, Rh
Appearance Silvery white metal
Rhodium in the periodic table
Co

Rh

Ir
RutheniumRhodiumPalladium
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)
· references

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 dense, with a value of 12.41 g/cm3.

Availability

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

It 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

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