Rhodium
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Rhodium, Rh | ||||
| Appearance | Silvery white metal | ||||
| Rhodium in the periodic table | |||||
| |||||
| 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.
Contents
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.
