Barium

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Symbol:

Ba

Atomic Number:

56

Relative Atomic Mass:

137.327 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

0.03% (mass fraction)

Electron Configuration:

[Xe]6s²

Oxidation States:

II

Atomic Radius:

217.4pm

Covalent Radius:

198pm

Ionic Radius:

135pm (for +2 oxidation state, 6 coordinate)

142pm (for +2 oxidation state, 8 coordinate)

Melting Point:

725°C

Density:

3.65 g cm^-3 (at 20°C)

First Ionisation Energy:

5.212 eV

Reduction Potential:

-2.912V

for Ba²⁺ +2e^- a Ba_(s)

Electronegativity (Allred and Rochow):

1.0

Number of Natural Isotopes:

7

Mass Number of the Most Abundant Isotopes:

136 g mol^-1 a 7.9% abundance

137 g mol^-1 a 11.2% abundance

138 g mol^-1 a 71.7% abundance