Calcium compounds: calcium carbonate

calcium symbol icon

The calcium in calcium carbonate formally is in the oxidation state 2.

Calcium carbonate

  • Formula as often written: CaCO3
  • Hill system formula: C1Ca1O3
  • CAS registry number: [471-34-1]
  • Formula weight: 100.087
  • Class: carbonate


  • calcium carbonate
  • calcium(II) carbonate
  • aragonite
  • chalk
  • limestone

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 825°C (decomposes to CaO + CO2)
  • Boiling point:
  • Density: 2830 kg m-3


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Element analysis

Element percentages for the elements in calcium carbonate
Element %
C 12.00
Ca 40.04
O 47.96


Calcium carbonate is not normally made as it is available as ores. Small samples of pure CaCO3 are made by the reaction of CaCl2 in water with ammonium carbonate/aqueous ammonia.

CaCl2(aq) + (NH4)2CO3(aq) → CaCO3(s) + 2NH4Cl(aq)

Isotope pattern

What follows is the calculated isotope pattern for the CaCO3 unit with the most intense ion set to 100%.

Formula: Ca1C1O3

mass  %
100 100.0 __________________________________________________
101 1.2 _
102 1.3 _
103 0.2
104 2.2 _
105 0.0
106 0.0
107 0.0
108 0.2
109 0.0


The data on these compounds pages are assembled and adapted from the primary literature and several other sources including the following.

  • R.T. Sanderson in Chemical Periodicity, Reinhold, New York, USA, 1960.
  • N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
  • F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
  • A.F. Trotman-Dickenson, (ed.) in Comprehensive Inorganic Chemistry, Pergamon, Oxford, UK, 1973.
  • R.W.G. Wyckoff, in Crystal Structures, volume 1, Interscience, John Wiley & Sons, 1963.
  • A.R.West in Basic solid state chemistry Chemistry, John Wiley & Sons, 1999.
  • A.F. Wells in Structural inorganic chemistry, 4th edition, Oxford, UK, 1975.
  • J.D.H. Donnay, (ed.) in Crystal data determinative tables, ACA monograph number 5, American Crystallographic Association, USA, 1963.
  • D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
  • J.W. Mellor in A comprehensive treatise on inorganic and theoretical chemistry, volumes 1-16, Longmans, London, UK, 1922-1937.
  • J.E. Macintyre (ed.) in Dictionary of inorganic compounds, volumes 1-3, Chapman & Hall, London, UK, 1992.

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calcium atomic number