55 Cs Caesium 132.91
Alkali metal
Caesium 铯
[Xe] 6s¹
- Period 6
- Group 1
- Block s
- Solid
Electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹
Orbital diagram (valence)
- Electrons per shell
- 2, 8, 18, 18, 8, 1
- Unpaired electrons
- 1
- Zeff (Slater)
- 2.20
Properties
- Atomic weight
- 132.91
- Electronegativity (Pauling)
- 0.79
- First ionization energy
- 375.7 kJ/mol
- Electron affinity
- 45.54 kJ/mol
- Covalent radius
- 244 pm
- van der Waals radius
- 343 pm
- Melting point
- 301.6 K
- Boiling point
- 944 K
- Density
- 1.93 g/cm³
- Melting / boiling point
- 28.4 °C / 670.9 °C
- Common oxidation states
- +1
- Discovered
- 1860
Caesium in the course
The lessons that discuss this element most (ranked by mentions).
Periodic trend
Data: PubChem periodic table (public domain); atomic weights are IUPAC abridged standard values; covalent radii from Cordero et al. (2008).