55 Cs
Alkali metal
Cesium
Defines the SI second.
Properties of Cesium
- Atomic number (Z)
- 55
- Symbol
- Cs
- Atomic mass
- 132.91 g/mol
- Category
- Alkali metal
- Group
- 1
- Period
- 6
- Electron configuration
- [Xe] 6s¹
- Electronegativity (Pauling)
- 0.79
- Atomic radius
- 298 pm
- First ionization energy
- 376 kJ/mol
- Melting point
- 301.59 K (28.4 °C)
- Boiling point
- 944 K (670.9 °C)
- Density
- 1.873 g/cm³
- Phase at 25 °C
- Solid
- Discovered
- Discovered in 1860
Frequently asked questions
What is Cesium?
Cesium (Cs) is an alkali metal, element number 55 on the periodic table. Defines the SI second.
What is the atomic number and atomic mass of Cesium?
Cesium has atomic number 55 and an atomic mass of about 132.91 g/mol.
What is the electron configuration of Cesium?
The electron configuration of Cesium is [Xe] 6s¹.
Where is Cesium on the periodic table?
Cesium sits in group 1, period 6, and is classified as a alkali metal.