Figure 1. Calcium, with atomic number 20 and atomic weight of 40.078.[1]

Calcium is the 20th element on the periodic table of elements and it is the fifth most abundant element in the earth's crust.[2] Some of its properties are listed below:[2]

Atomic weight 40.078
Density (at 0oC) 1.54 g/cm3
Boiling point 1757 K
Melting point 1115 K

Calcium is an alkaline Earth mineral. It is naturally found in bones, teeth, shells, rocks, and minerals. Calcium carbonate is a naturally occurring compound that is the basis for limestone, marble, and chalk. Stalagmites and stalactites in caves form from calcium carbonate precipitating out of solution.[3]

Calcium uses

Calcium is used as a reducing and/or alloying agent for metals[2]. It is used primarily in the creation of steel to improve the steel's mechanical properties. Historically, calcium was used to create lime (a calcium oxide and/or hydroxide compound), which was used as a building material. Lime is still used today in substances like paints, concrete, cement, and plaster.

Calcium compounds (such as calcium carbonate or calcium magnesium pills) are often used as calcium supplements for human consumption. Calcium carbonate is also used as an antacid for indigestion[3].

Calcium Carbonate as part of the Carbon Dioxide Cyle

Calcium carbonate compounds (limestone, shells, etc.) are natural carbon sinks in two ways:[4]

  • The formation of carbonate (CO3) often involves the capture of CO2
  • Calcium carbonate can react with carbon dioxide saturate water and for calcium bicarbonate (Ca(HCO3)2)

Through weathering and human activities, the calcium carbonate can be made to break down, releasing the stored carbon dioxide. Acidified solutions (e.g. acid rain) and heat (especially from human processign) are particularly good at breaking down calcium carbonate and bicarbonate into calcium oxide and carbon dioxide (and water, in the case of bicarbonate breakdown)[4].


Calcium has six isotopes found in nature:[2]

Symbol Natural Abundance
40Ca 96.941%
42Ca 0.647%
43Ca 0.135%
44Ca 2.086%
46Ca 0.004%
48Ca 0.187%


The video below is from the University of Nottingham's periodic videos project.[5] They have created a complete suite of short videos on every element on the periodic table of elements.

For Further Reading


  1. Made internally by a member of the Energy Education team, with information from, Available:
  2. 2.0 2.1 2.2 2.3 Royal Society of Chemistry Periodic Table, Calcium [Online], Available:
  3. 3.0 3.1 John Emsley, "Nature’s Building Blocks: An A-Z Guide to the Elements", Oxford University Press, New York, 2nd Edition, 2011.
  4. 4.0 4.1 John W. Morse, Rolf S. Arvidson, and Andreas Lüttge. "Calcium Carbonate Formation and Dissolution". Chemical Reviews, 2007, V.107 (2), pg 342-381.
  5. See more videos from the University of Nottingham on different elements here:

Authors and Editors

Ashley Sheardown, Jason Donev
Last updated: January 4, 2019
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