Caesium compounds: caesium chloride

caesium symbol icon

The caesium in caesium chloride formally is in the oxidation state 1.

Crystal structure of caesium chloride

Caesium chloride

  • Formula as often written: CsCl
  • Hill system formula: Cl1Cs1
  • CAS registry number: [7647-17-8]
  • Formula weight: 168.358
  • Class: chloride


  • caesium chloride
  • caesium(I) chloride
  • cesium chloride
  • cesium(I) chloride

Physical properties

  • Colour: white
  • Appearance: crystalline solid
  • Melting point: 646°C
  • Boiling point: 1290°C; 1297°C
  • Density: 3988 kg m-3


Coming soon...

Element analysis

Element percentages for the elements in caesium chloride
Element %
Cl 21.06
Cs 78.94


One way to make caesium chloride is to react the hydroxide with hydrochloric acid. The resulting salt can then be purified by recrystallization.

CsOH(aq) + HCl(aq) → CsCl(aq) + H2O(l)

Caesium(I) chloride can also be made by the neutralization of caesium(I) carbonate with hydrochloric acid. The resulting salt can then be purified by recrystallization.

Cs2(CO3)(aq) + 2HCl(aq) → 2CsCl(aq) + H2O(l) + CO2(g)

While not a normal route of preparation because of the expense, caesium metal reacts vigorously with all the halogens to form sodium halides. So, it burns with chlorine, Cl2, to form caesium(I) chloride, CsCl.

2Cs(s) + Cl2(g) → 2CsCl(s)

Solid state structure

  • Geometry of caesium: 8 coordinate: cubic
  • Prototypical structure: CsCl

Crystal structure of caesium chloride

Isotope pattern

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

Formula: Cs1Cl1

mass  %
168 100.0 __________________________________________________
169 0.0
170 32.0 ________________


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.

WebElements Shop

WebElements now has a WebElements shop at which you can buy periodic table posters, mugs, T-shirts, games, fridge magnets, molecular models, and more.

Periodic Table fridge magnets Periodic Table fridge magnets
Buy our periodic table fridge magnets here

WebElements poster Periodic table t-shirts Periodic table mouse mats Molymod molecular model kits Chemistry educational resources

caesium atomic number