Stable isotope Caesium (Cs)

Isotope Z(p) N(n) Atomic Mass Natural Abundance Nuclear Spin
Cs-133 55 78 132.905447 100.00%  7/2+

Properties of Cesium

Name Cesium
Symbol Cs
Atomic number 55
Atomic weight 132.905
Standard state Solid at 298 ºK (but melts only slightly above this temperature)
CAS Registry ID 7440-46-2
Group in periodic table 1
Group name Alkali metal
Period in periodic table 6
Block in periodic table s-block
Color Silvery gold
Classification Metallic
Melting point 28.44 °C
Boiling point 669.3 °C
Thermal conductivity 35.9 W/(m·K) at 298.2 °K
Electrical resistivity 20 µΩ·cm at 20 °C
Electronegativity 0.7
Specific heat 242 J/kg K
Heat of vaporization 65 kJ·mol-1
Heat of fusion 2.09 kJ·mol-1
Density of liquid 1.843 g/cm3
Density of solid 1.93 g/cm3
Mohs hardness scale 0.2
Electron configuration [Xe]6s
Atomic radius 2.65 Å
Ionic radius Cs+: 1.84 Å
Oxidation state +1
Ionization potential 3.89 eV