Periodic Table of Elements

55

Caesium

132.91

Caesium was discovered by German chemists, Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, in 1860 by the newly developed method of flame spectroscopy.

Name: Caesium
Symbol: Cs
Atomic number: 55
Atomic weight: 132.91
State: solid
Group, period, block: 1, 6, s
Color: silvery gold
Classification: alkali metal
Electron configuration: 6s1
2,8,18,18,8,1

Physical properties

Density: 1.93 g/cm-3
Melting point: 301.59 K, 28.44 C, 83.19 F
Boiling point: 944 K, 671 C, 1240 F

Atomic properties

Oxidation states: 1
Electronegativity: 0.79 (Pauling scale)
Ionization energies: 1st: 375.7 kJmol-1
Covalent radius: 24411 pm
Van der Waals radius: 343 pm
  • Cs
  • Electron Configuration

Isotopes

There is one naturally occurring isotope of caesium exists, 133Cs.