Calcium carbonate

  • Formula: CaCO3
  • Hill system formula: C1Ca1O3
  • CAS registry number: [471-34-1]
  • Formula weight: 100.087
  • Class: carbonate
  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 825°C (decomposes to CaO + CO2)
  • Boiling point:
  • Density: 2830 kg m-3

The following are some synonyms of calcium carbonate:

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

The oxidation number of calcium in calcium carbonate is 2.


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)

Element analysis

The table shows element percentages for CaCO3 (calcium carbonate).

Element %
C 12.00
Ca 40.04
O 47.96

Isotope pattern for CaCO3

The chart below shows the calculated isotope pattern for the formula CaCO3 with the most intense ion set to 100%.


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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