Periodic Table
55
Cs
132.91
Caesium
Alkali MetalMost reactive (non-radioactive) metal; defines the second; lowest IE (practically).
Electronic Configuration
[Xe] 6s¹or1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹
Electron shells
2e⁻n=1
8e⁻n=2
18e⁻n=3
18e⁻n=4
8e⁻n=5
1e⁻n=6
Properties
Atomic number
55
Atomic mass
132.91 u
Category
Alkali Metal
Block / Group / Period
s · 1 · 6
Valence electrons
1
Oxidation states
+1
Electronegativity
0.79
Atomic radius
298 pm
Ionization energy
376 kJ/mol
Electron affinity
46 kJ/mol
Melting point
302 K / 29 °C
Boiling point
944 K / 671 °C
Density
1.873 g/cm³
State at 25 °C
solid
Personal Notes
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