Rhodium (Rh)

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Rhodium 45Rh102.905

Discovered in 1803 by W.H. Wollaston at London, England.

[Greek, rhodon = rose]

French: rhodium
German: Rhodium
Italian: rodio
Spanish: rodio

Description: Rhodium is a rare, lustrous, silvery, hard metal of the so-called platinum group. It is unaffected by air and water up to 875 K, and unaffected by acids, but is attacked by molten alkalis. Rhodium is used as a catalyst.



Rhodium single crystal properties

State: single crystal
Crystal structure: fcc
Production method: Floating Zone
Standard size: diameter 6-10mm
thickness 1-2mm
Orientation: (100), (110) and (111)
Orientation accuracy: <2°, <1°, <0.4° or <0.1°
Polishing: as cut, one or two sides polished
Roughness of surface: <0.03µm
Purity: 99.99%
Typical analysis (ppm): C 3
H < 1
O 9
N < 5
Cu 1.60
Fe 1.80
Ni < 1
Pb 0.30
Si 0.30

Ga, Hf and Ta are below the detection limit

Materials properties

Density: 12.4 g/cm3
Melting point: 1965.85 °C / 2239 °K
Boiling point: 3726.85 °C / 4000 °K
Molar volume: 8.29 cm3
Thermal conductivity: 150 [300 K] Wm-1K-1
Coefficient of linear thermal expansion: 8.40 x 10-6 K-1
Electrical resistivity: 4.51x 10-8 [293 K] Wm
Mass magnetic susceptibility: +1.36 x 10-8(s) kg-1m3
Young's modulus: 379 GPa
Rigidity modulus: 147 GPa
Bulk modulus: 276 GPa
Poisson's ratio: 0.26
Radii: Rh4+ 67; Rh3+ 75; Rh2+ 86; atomic 134; covalent 12
Electronegativity: 2.28 (Pauling); 1.45 (Allred); 4.30 eV (absolute)
Effective nuclear charge: 3.90 (Slater); 7.64 (Clementi); 10.85 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 34
Issotope mass range: 94m -> 112
Crystal structure, (cell dimentions / pm), space group fcc
X-ray diffraction: mass absorption coefficients: CuKα 194 (µ/r) / cm2g-1
MoKα 22.6 (µ/r) / cm2g-1
Neutron scattering length: 0.588 b/10-12 cm
Thermal neutron capture cross-section: 144.8 sa / barns


Biological data

Biological role: none
Toxic intake: most rhodium compounds are slightly toxic by ingestion.
Lethal intake: LD50 (RhCl3, ortal, rat)= 12.6 mg kg-1
Hazards: There are few reported cases of humans being affected by rhodium, but it is an experimental carcinogen.
Level in humans  
Daily dietary intake: n.a.
Total mass of element in average [70 kg] person: n.a.


Geological data

MineralFormulaDensityHardnessCrystal apperance
Rhodium Rh c. 12 3.5 cub., met. white
Rhodplumsite Ph3Pb2S2 9.74 n.a. rhom., met. cream-pink/grey-blue


Chief ore: native rhodium is found in Montana, USA; certain copper and nickel ores contain up to 0.1% rhodium a
World production: 3 tonnes/year
Main mining areas: see copper and nickel
Reserves: n.a.
Specimen: available as foil, sponge or wire. Safe.


Sun: 25.1 (relative to H = 1 x 1012)
Earth's crust: 2 x 10-4 p.p.m.
Residence time:  
Oxidation state:  

Source: Emsley, J. (1998) The Elements (3rd Edition)

Overview of elements with access to our shop

1 18
2 13 14 15 16 17
Li Be B C
Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se
Rb Sr Y Zr Nb Mo
Ru Rh Pd Ag Cd In Sn Sb Te I
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi
Ce Pr Nd
Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

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