Cesium
Alkali Metal
Cesium (Cs) is a chemical element with atomic number 55, classified as a alkali metal. At room temperature it is a solid. It was discovered in 1860 by Robert Bunsen, Gustav Kirchhoff.
Properties
- Atomic number
- 55
- Atomic mass
- 132.91 u
- Category
- Alkali Metal
- Group
- 1
- Period
- 6
- Block
- s-block
- Electron configuration
- [Xe] 6s¹
- Phase at STP
- Solid
- Density
- 1.873 g/cm³
- Melting point
- 301.59 K (28.4 °C)
- Boiling point
- 944 K (670.9 °C)
- Electronegativity
- 0.79
- Atomic radius
- 298 pm
- Ionization energy
- 3.894 eV
- Discovery
- 1860 · Robert Bunsen, Gustav Kirchhoff
Common uses
Atomic clocks, photoelectric cells, catalysts, drilling fluids
Did you know?
Melts in warm weather and defines the second in atomic time.