Calcium

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Symbol:

Ca

Atomic Number:

20

Relative Atomic Mass:

40.078 g mol^-1

Natural Abundance in Lithosphere, hydrosphere and atmosphere:

3.39% (mass fraction)

Electron Configuration:

[Ar]4s²

Oxidation States:

I

Atomic Radius:

197.4pm

Covalent Radius:

174pm

Ionic Radius:

100pm (for +2 oxidation state, 6 coordinate)

112pm (for +3 oxidation state, 8 coordinate)

Melting Point:

839°C

Density:

1.54 g cm^-3 (at 20°C)

First Ionisation Energy:

6.113 eV

Reduction Potential:

-2.87V

for Ca²⁺ +2e^- a Ca_(s)

Electronegativity (Allred and Rochow):

1.0

Number of Natural Isotopes:

6

Mass Number of the Most Abundant Isotopes:

40 g mol^-1 a 96.9% abundance

42 g mol^-1 a 0.6% abundance

44 g mol^-1 a 2.1% abundance