Cesium (Cs) - Properties, Applications

Topics Covered

Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties


Cesium is silvery gold in appearance, soft and ductile by nature. It is the most alkaline and the most electronegative element. It is in the liquid state at room temperature. The atomic number of cesium is 55 and it belongs to the alkali metal category. It belongs to s-block, period 6 element in the periodic table.

Cesium is comparitively rare when compared to other alkali metals. It is primarily distributed in Zimbabwe, Canada and South-West Africa. There are very few minerals of cesium, namely, pollucite and silicate magmas that are cooled from granites. Cesium exhibits radioactivity and hence limited exposure is safe for humans.

Chemical Properties

The chemical properties of Cesium are provided in the table below:

Chemical Data
CAS number 7440-46-2
Thermal neutron cross section 29 barns/atom
Electrode potential -3.00 V
Ionic radius 1.67 Å
Electro negativity 0.79
X-ray absorption edge 0.34476 Å
Electrochemical equivalent 4.957 g/A/h

Physical Properties

The following table discusses the physical properties of Cesium.

Properties Metric Imperial
Density 1.89 g/cm3 0.0683 lb/in3
Melting point 28.55 °C 83.39 °F
Boiling point 671°C 1240°F

Mechanical Properties

The mechanical properties of Cesium are tabulated below.

Properties Metric Imperial
Bulk Modulus 1.57 GPa 228 ksi

Thermal Properties

The thermal properties of Cesium are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20°C/68°F) 97 µm/m°C 53.9 µin/in°F
Thermal conductivity 36.0 W/mK 250 BTU in/hr.ft².°F


The following are the application areas of Cesium:

  • Catalyst promoter
  • Remove oxygen from vacuum tubes and light bulbs
  • Atomic clocks
  • Petroleum exploration
  • Centrifugation fluids
  • Chemical and medicinal uses.

Cesium compounds are used in the manufacture of optical glasses and photoelectric cells.

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