Caesium (Cs)
Caesium
Caesium (Cs) is an alkali metal in period 6, group 1. Its relative atomic mass is 132.91 and the molar mass of the atom is 132.91 g/mol.
Atomic number 55
Atomic mass 132.91
Molar mass 132.91 g/mol
Category Alkali metal Solid
Properties of caesium
| Atomic number | 55 |
|---|---|
| Symbol | Cs |
| Latin name | Caesium |
| Relative atomic mass | 132.91 |
| Molar mass | 132.91 g/mol |
| Group, period, block | 1, 6, s |
| Category | Alkali metal |
| State at 20 °C | Solid |
| Electron configuration | [Xe] 6s¹ |
| Electronegativity (Pauling) | 0.79 |
| Atomic radius | 260 pm |
Electron configuration of caesium
Electrons per shell
K2L8M18N18O8P1
Full notation
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹
Noble-gas notation
55 protons · 55 electrons[Xe] 6s¹
Formula and compounds of caesium
Simple substanceCscaesiumMolar mass of Cs: 132.91 g/mol
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Frequently asked questions
The relative atomic mass of caesium is 132.91, so the molar mass of the atom is 132.91 g/mol.
Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹. Noble-gas notation: [Xe] 6s¹.