Living Reference Work Entry

Encyclopedia of Geochemistry

Part of the series Encyclopedia of Earth Sciences Series pp 1-5

Date: Latest Version


  • Christophe LécuyerAffiliated withLaboratoire de Géologie de Lyon, LGL-TPE, CNRS UMR 5276, Université Claude Bernard Lyon 1Institut Universitaire de France Email author 

Element Data

Atomic Symbol: Ca

Atomic Number: 20

Atomic Weight: 40.078(4)

Isotopes and Abundances: 40Ca, 96.941(156)%; 42Ca, 0.647(23)%; 43Ca, 0.135(10)%; 44Ca, 2.086(110)%; 48Ca, 0.187(21)%

1 Atm Melting Point: 840 °C

1 Atm Boiling Point: 1,484 °C

Common Valences: +2

Ionic Radii: 6-fold: 114 pm

Pauling Electronegativity: 1.00

First Ionization Potential: 589.83 kJ.mol−1

Chondritic (CI) Abundance: 9,110 ppm (59,820 atoms/106 Si)

Silicate Earth Abundance: 25,300 ppm

Crustal Abundance: 41,500 ppm

Seawater Abundance: 412 to 420 ppm

Core Abundance: ~0


Calcium is a metal (alkaline earth) with a silvery color and a cubic crystal structure. This element belongs to group 2 and period 4 of the periodic table (Figure 1). Calcium has 25 known isotopes of which 5 are stable (source of data: National Institute of Standards and Technology: http://​www.​nist.​gov/​pml/​data/​comp.​cfm).
Figure 1

Schematic illustration of the atomic configuration of 40Ca.

Geochemists measure the relative ...

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