Atomic Element Z = 55 • Alkali Metal
Cesium (Cs) — Atomic Data, Electron Shells & Reactions
Cesium (symbol Cs, atomic number 55) has a standard atomic weight of 132.91 u and ground-state configuration [Xe] 6s1.
Atomic Number (Z)
55
IUPAC Symbol
Cs
Standard Atomic Weight
132.91 g/mol
Period / Group / Block
6 / 1 / s-block
Condensed Electron Config
[Xe] 6s1
Full Subshell Config
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s1
Principal Shell Occupancy
[2, 8, 18, 18, 8, 1]
Pauling Electronegativity
0.79
First Ionization Energy
376 kJ/mol
Covalent Radius
244 pm
Melting Point
301.7 K (28.55 °C)
Boiling Point
944 K (670.85 °C)
Density
1.873 g/cm³
Oxidation States
+1
Cs (Z=55) — Valence shell highlighted in vermilion