iridium

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Symbol:

Ir

Atomic Number:

77

Relative Atomic Mass:

192.217 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

10^-7% (mass fraction)

Electron Configuration:

[Xe]4f¹⁴5d⁷6s²

Oxidation States:

VI, IV, III, II, I, 0, -I

Atomic Radius:

135.7pm

Covalent Radius:

127pm

Ionic Radius:

63pm (for +4 oxidation state)

68pm (for +3 oxidation state)

Melting Point:

2410°C

Density:

22.65 g cm^-3 (at 20°C)

First Ionisation Energy:

9.1 eV

Reduction Potential:

1.156V

for Ir³⁺ + 3e^- a Ir_(s)

Electronegativity (Allred and Rochow):

1.6

Number of Natural Isotopes:

2

Mass Number of the Most Abundant Isotopes:

191 g mol^-1 a 37.3% abundance

193 g mol^-1 a 62.7% abundance