Caesium
Caesium (铯, symbol Cs) is chemical element number 55, an Alkali Metal in period 6, group 1 of the periodic table, with a standard atomic weight of about 132.91. Soft, gold-colored alkali metal. The basis of the SI second through atomic clocks.
Properties
| Atomic number | 55 |
|---|---|
| Symbol | Cs |
| Atomic mass | 132.91 u |
| Category | Alkali Metal |
| Period | 6 |
| Group | 1 |
| Electron configuration | [Xe] 6s¹ |
| Electronegativity | 0.79 |
| Covalent radius | 244 pm |
| Density | 1.873 g/cm³ |
| Melting point | 301.59 K |
| Boiling point | 944 K |
| Discovery | Bunsen & Kirchhoff, 1860 |
Overview
Soft, gold-colored alkali metal. The basis of the SI second through atomic clocks. Caesium (Cs) holds position 55 in the periodic table, an Alkali Metal in period 6, group 1. As an alkali metal it is soft and highly reactive, releasing hydrogen on contact with water, and is usually stored away from air and moisture.
With 1 electron in its outermost shell, Caesium bonds accordingly; full configuration [Xe] 6s¹, electronegativity 0.79. At room temperature it is normally a solid (a very low melting point); it melts near 301.59 K (28.4 °C), boils near 944 K (670.9 °C), has a density around 1.873 g/cm³.
Common applications range across Research and Electronics / Semiconductors. On the safety side, it carries a moderate hazard rating. It was first described by Bunsen & Kirchhoff in 1860. Browse elements of the same category in the browse view.
Electron shells
Electrons per shell: 2 · 8 · 18 · 18 · 8 · 1
Main uses
- Research
- Electronics / Semiconductors
Hazard
Compounds containing Caesium
No compounds in this knowledge base contain Caesium yet.
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.