Cs
Cesium is the most electropositive stable element and defines the second in atomic clocks.
Physical Properties
| Atomic Mass | 132.91 u |
| Density | 1.873 g/cm³ |
| Melting Point | 301.59 K |
| Boiling Point | 944.0 K |
| Appearance | Silvery gold metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 0.79 (Pauling) |
| 1st Ionization Energy | 375.7 kJ/mol |
| Electron Affinity | 45.5 kJ/mol |
| Oxidation States | +1 |
Atomic Properties
| Electron Configuration | [Xe] 6s1 |
| Atomic Radius | 265.0 pm |
| Covalent Radius | 244.0 pm |
| Van der Waals Radius | 343.0 pm |
Discovery
| Discovered By | Robert Bunsen, Gustav Kirchhoff |
| Discovery Year | 1860 |
| Location | Heidelberg, Germany |
| Named After | Latin 'caesius' meaning sky blue, from its spectral lines |
About Cesium
Cesium is a soft, silvery-gold alkali metal with a melting point of 28.44 degrees C. It is extremely reactive and pyrophoric. Cesium-133 defines the second in the SI system.
Uses & Applications
Atomic clocks, drilling fluids, photoelectric cells, and radiation therapy.
Fun Fact
The official definition of one second is exactly 9,192,631,770 oscillations of the cesium-133 atom.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 133 | 1.0% | - | Yes |
Electron Configuration
[Xe] 6s1