|
45
Rh
102.9
|
Catalyst for ethanol oxidation:
platinum-rhodium clusters on a surface of tin dioxide.
This catalyst can split the carbon-carbon bond and obtain energy from ethanol in fuel cells.
Photo: BNL
| Classification: | Rhodium is a transition metal |
| Color: | silvery-white |
| Atomic weight: | 102.9055 |
| State: | solid |
| Melting point: | 1963 oC, 2236 K |
| Boiling point: | 3695 oC, 3968 K |
| Shells: | 2,8,18,16,1 |
| Electron configuration: | [Kr] 4d8 5s1 |
| Density @ 20oC: | 12.4 g/cm3 |
| Atomic volume: | 8.3 cm3/mol |
| Structure: | fcc: face-centered cubic |
| Hardness: | 6.0 mohs |
Discovery of Rhodium
Rhodium was discovered by William Hyde Wollaston in 1803 in crude platinum ore.
Wollaston removed platinum and palladium from the ore to leave a red salt - sodium rhodium chloride [RhCl6]Na3.12H2O from which he extracted rhodium metal.
The element name comes from the Greek word 'rhodon' meaning rose.
Appearance & Characteristics
Rhodium pin and foil. Photo by Dschwen.
Harmful effects:
Rhodium is considered to be non-toxic. Some of its compounds are highly toxic and carcinogenic.
Characteristics:
Rhodium is a rare, hard, silvery-white, lustrous metal. It is highly reflective and extremely resistant to corrosion. It is not attacked by most acids. Rhodium's salts form rose-colored aqueous solutions.
The majority of rhodium is used as a catalyst in catalytic converters. It is also used to catalyze industrial processes. Rhodium is used as an alloying agent for hardening and improving the corrosion resistance of platinum and palladium. As a result of its low electrical resistance, low and stable contact resistance, and its stability against corrosion rhodium is used as an electrical contact material. The metal is used in jewelry and for decorations.
Rhodium is considered to be non-toxic. Some of its compounds are highly toxic and carcinogenic.
Characteristics:
Rhodium is a rare, hard, silvery-white, lustrous metal. It is highly reflective and extremely resistant to corrosion. It is not attacked by most acids. Rhodium's salts form rose-colored aqueous solutions.
Uses of Rhodium
The majority of rhodium is used as a catalyst in catalytic converters. It is also used to catalyze industrial processes. Rhodium is used as an alloying agent for hardening and improving the corrosion resistance of platinum and palladium. As a result of its low electrical resistance, low and stable contact resistance, and its stability against corrosion rhodium is used as an electrical contact material. The metal is used in jewelry and for decorations.
Abundance & Isotopes
Abundance earth's crust: 1 part per billion by weight, 0.1 parts per billion by moles
Abundance solar system: 2 parts per billion by weight, 0.02 parts per billion by moles
Cost, pure: $13,000 per 100g
Cost, bulk: $7,000 per 100g
Source: Rhodium occurs in small quantities in ores metals such as platinum, palladium, nickel, silver, and gold. Commercially, it is obtained as a byproduct of refining nickel sulfide ores from Canada.
Isotopes: Rhodium has 24 isotopes whose half-lives are known, with mass numbers from 94 to 117. Of these, only one is stable, 103Rh.
Abundance solar system: 2 parts per billion by weight, 0.02 parts per billion by moles
Cost, pure: $13,000 per 100g
Cost, bulk: $7,000 per 100g
Source: Rhodium occurs in small quantities in ores metals such as platinum, palladium, nickel, silver, and gold. Commercially, it is obtained as a byproduct of refining nickel sulfide ores from Canada.
Isotopes: Rhodium has 24 isotopes whose half-lives are known, with mass numbers from 94 to 117. Of these, only one is stable, 103Rh.
Energies
Specific heat capacity: 0.242 J g-1 K-1
Heat of fusion: 21.50 kJ mol-1
1st ionization energy: 719.8 kJ mol-1
3rd ionization energy: 2996.8 kJ mol-1
Heat of fusion: 21.50 kJ mol-1
1st ionization energy: 719.8 kJ mol-1
3rd ionization energy: 2996.8 kJ mol-1
Heat of atomization: 556 kJ mol-1
Heat of vaporization: 493.0 kJ mol-1
2nd ionization energy: 1744.4 kJ mol-1
Electron affinity: 109.7 kJ mol-1
Heat of vaporization: 493.0 kJ mol-1
2nd ionization energy: 1744.4 kJ mol-1
Electron affinity: 109.7 kJ mol-1
Oxidation & Electrons
Shells: 2,8,18,16,1
Minimum oxidation number: -1
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 2.28
Minimum oxidation number: -1
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 2.28
Electron configuration: [Kr] 4d8 5s1
Maximum oxidation number: 6
Max. common oxidation no.: 3
Polarizability volume: 8.6 Å3
Maximum oxidation number: 6
Max. common oxidation no.: 3
Polarizability volume: 8.6 Å3
Reactions & Compounds
Reaction with air: mild, w/ht, ⇒ Rh2O3
Reaction with 15 M HNO3: none
Oxide(s): RhO2, Rh2O3
Hydride(s): none
Reaction with 15 M HNO3: none
Oxide(s): RhO2, Rh2O3
Hydride(s): none
Reaction with 6 M HCl: none
Reaction with 6 M NaOH:
Chloride(s): RhCl3
Reaction with 6 M NaOH:
Chloride(s): RhCl3
Radius
Atomic radius: 134 pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 80.5 pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): 80.5 pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 150 W m-1 K-1
Electrical conductivity:23 x 106 S m-1
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