osmium

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Symbol:

Os

Atomic Number:

76

Relative Atomic Mass:

190.23 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

10^-6% (mass fraction)

Electron Configuration:

[Xe]4f¹⁴5d⁶6s²

Oxidation States:

VIII, VI, IV, III, II, 0, -II

Atomic Radius:

133.8pm

Covalent Radius:

126pm

Ionic Radius:

39pm (for +8 oxidation state)

63pm (for +4 oxidation state)

Melting Point:

3045°C

Density:

22.61 g cm^-3 (at 20°C)

First Ionisation Energy:

8.7 eV

Reduction Potential:

0.85V

for OsO₄ + 8H⁺ + 8e^- a Os_(s) + 4H₂O

Electronegativity (Allred and Rochow):

1.5

Number of Natural Isotopes:

7

Mass Number of the Most Abundant Isotopes:

189 g mol^-1 a 16.1% abundance

190 g mol^-1 a 26.3% abundance

192 g mol^-1 a 40.8% abundance