Osmium (Os)

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Osmium 76Os190.23

Discovered 1803 by S. Tennant at London, England.

[Greek, osme = smell]

French: osmium
German: Osmium
Italian: osmio
Spanish: osmio

Description: Osmium is a lustrous, silvery metal of the so-called platinum group. It is unaffected by air, water, and acids, but dissolves in molten alkalis. Osmium metal gives off a recognizable smell due to the formation of volatile osmium tetroxide, OsO4. The metalis used in alloys and catalysts.


Further Materials properties


Crystal structure:

(cell dimensions/pm), space group, 
h.c.p. (a=273.43, c=432.00), P63/mmc

X-ray diffractions mass absorption coefficients: CuKa 186 (µ/r) / cm2g-1
MoKa 106 (µ/r) / cm2g-1
Neutron scattering length: 1.07 b/10-12 cm
Thermal neutron capture cross-section: 15 sa / barns
Density: 22 590 kg/m-3 [293 K]
Melting point: 3053.85°C / 3327°K
Boiling point: 5026.85°C / 5300°K
Molar volume: 8.43 cm3
Thermal conductivity: 87.6 [300 K] W m-1K-1
Coefficient of linear thermal expansion: 4.3 x 10-6 (a axis); 6.1 x 10-6 (b axis); 6.8 x 10-6 (c axis) K-1
Electrical resistivity: 8.12 x 10-8 [273 K] Ωm
Mass magnetic susceptibility: +6.5 x 10-10(s) kg-1m3
Radi: Os4+ 67; Os3+ 81; Os2+ 89; atomic 135; covalent 126
Electronegativity: 2.2 (Pauling); 1.52 (Allred); 4.9 eV (absolute)
Effective nuclear charge: 3.75 (Slater); 10.32 (Clementi); 14.90 (Froese-Fischer)
Number of Isotopes (incl. nuclear isomers): 37
Isotope mass range: 166 -> 196



Biological data


Biological role: None.
Toxicity The metal itself is not toxic but its volatile oxide, OsO4, is.
Toxic intake: oxide, inhalation, human = 133 µg m-3
Lethal intake: LD50 (oxide, oral, rat) = 162 mg kg-1
Hazards: Osmium dust is an irritant to eyes, skin and mucous membranes.
Level in humans n.a. but very low
Daily dietary intake: n.a. 
Total mass of element in average
[70 kg] person:
n.a. but very low


Geological data


Minerals:Found in free state and as alloy with iridium.
MineralFormulaDensityHardnessCrystal apperance
Osmiridium  (Ir,Os) c. 20  6 - 7  cub. met. white
Osmium  Os 22.48  7  hex. met. white

Chief ores: obtained as a by-product of nickel refining
World production: 0.06 tonnes/year
Producing areas: see nickel
Reserves: n.a.
Specimen: available as powder or sponge. Danger!


Sun: 5 (relative to H = 1 x 1012)
Earth's crust: c. 1 x 10-4 ppm
Seawater n.a. but minute

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

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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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