55Cs132.91
Caesium (Cs)
Element 55 Ā· Alkali metal
Caesium (Cs) is a chemical element with atomic number 55. It is classified as an alkali metal in period 6, group 1 of the periodic table (the s-block). Its standard atomic weight is 132.91 u and its ground-state electron configuration is [Xe] 6sĀ¹.
Caesium facts
| Atomic number (Z) | 55 |
|---|---|
| Symbol | Cs |
| Standard atomic weight | 132.91 u |
| Category | Alkali metal |
| Group | 1 |
| Period | 6 |
| Block | s-block |
| Electron configuration | [Xe] 6sĀ¹ |
| Electronegativity (Pauling) | 0.79 |
| State at 20 Ā°C | Solid |
| Protons / electrons | 55 / 55 |
| Neutrons (most common isotope, approx.) | 78 |
| Molar mass | 132.91 g/mol |