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55
Cs
132.91
Caesium
Alkali metals · Group 1 · Period 6
Atomic properties
| Atomic number | 55 |
|---|---|
| Symbol | Cs |
| Standard atomic weight | 132.91 |
| Classification | Alkali metals |
| Group | 1 |
| Period | 6 |
| Block | s-block |
| Electron configuration | [Xe] 6s1 |
| Electronegativity (Pauling) | 0.79 |
| Common oxidation states | +1 |
Physical properties
| Phase at 20 °C | Solid |
|---|---|
| Density | 1.93 g/cm³ |
| Melting point | 28.44 °C |
| Boiling point | 671 °C |
| Discovered | 1860 |
| CAS number | — |