Latin nameCaesium
English nameCesium
chemical symbolCs
atomic number55
relative atomic mass132,90543
classificationalkali metals
discovery year1860
discovererBunsen, Kirchhoff
melting point [°C]28,4
boiling point [°C]669,3
critical temperature [°C]1665
critical pressure [MPa]9,4
density [g cm-3]1,873
density at melting point [g cm-3]1,843
electronegativity [Pauling]0,79
stand. el. potential [V]−3,026
oxidation statesI
electron configuration[Xe] 6s1
atomic radius [pm]298
covalent radius [pm]225
specific heat [J g-1K-1]0,24
heat of fusion [kJ mol-1]2,092
thermal conductivity [W m-1 K-1]35,9
el. conductivity [S m-1]5,3.106
1. ionizing potential [eV]3,8939
2. ionizing potential [eV]25,10
Mohs hardness0,2
Young's modulus [GPa]1,7
state at normal conditionssolid

Cesium is a silvery white to silvery gold metal. It is soft and ductile. Cesium is the most electropositive metal and bonds ionically with a wide variety of anions to form compounds.