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Atomic mass, symbol and atomic number
cesium is a naturally occurring element with the element symbol Cs and atomic number 55. In the periodic table it stands with an atomic mass of 132.90 u in the 1st main group. The chemical element discovered by Robert Bunsen in 1861 is not radioactive and is in a solid state of aggregation at room temperature.
Profile: Cesium (English cesium)
| General | |
|---|---|
| Chemical element: | cesium |
| Symbol: | Cs |
| Atomic number: | 55 |
| Group: | Alkali metals group |
| Period: | 6 |
| Block: | s block |
| Series: | alkali metals |
| Appearance: | hellsilber |
| explorers: | Robert Wilhelm Bunsen |
| Year of discovery: | 1861 |
| Atomic properties | |
| Atomic mass: | 132,905 u |
| Atomic radius: | 265 pm |
| Covalent radius: | 244 pm |
| Van der Waals radius: | 343 pm |
| Electron configuration: | Xe 6s1 |
| ionization: | 375.7 kJ / mol |
| Physical Properties | |
| Physical state: | firmly |
| Density: | ??? |
| Crystal structure: | cubic |
| Magnetism: | paramagnetic |
| molar volume: | 70,94 · 10-6 m3/ mol |
| Mohs hardness: | 0,2 |
| Melting point: | 28 ° C |
| Boiling point: | 690 ° C |
| Heat of fusion: | 2.09 kJ / mol |
| Heat of vaporization: | 66.1 kJ / mol |
| Thermal conductivity: | 36 W |
| Chemical properties | |
| electronegativity: | 0,79 |
Did you know that ...
- Robert Bunsen and Gustav Kirchhoff discovered the element as they studied mineral water?
- out of a total of 39 known isotopes only the isotope 133Cs naturally occurring on Earth?
- Cesium with a Mohs hardness of 0.2 is the softest of all elements?
- Due to the reactor accident in Fukushima (Japan), large parts of the city are contaminated with radioactive cesium?
- elemental cesium is highly flammable and can explode on contact with air?
