Caesium (Cesium) - ASCII Periodic Table of the Elements

ASCII PERIODIC TABLE OF THE ELEMENTS

  Cs

Relative atomic mass: 132.9054519 ± 0.0000002

English: Caesium (Cesium)
French: Césium
Croatian: Cezij
German: Cäsium
Italian: Cesio
Spanish: Cesio

Atomic number: 55
Group numbers: 1
Period: 6
Standard state (20 °C): solid

Discovery: 1860 Robert Wilhelm Bunsen, Gustav Robert Kirchhoff (DE)

Caesium (or cesium) was discovered by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff (DE) in 1860. The origin of the name comes from the Latin word 'caesius' meaning 'sky blue' or 'heavenly blue'. It is a very soft, light grey, ductile metal that reacts readily with oxygen and reacts explosively with water. Caesium is found in pollucite [(Cs4Al4Si9O26).H2O] and as trace in lepidolite. It is used as a 'getter' to remove air traces in vacuum and cathode-ray tubes, in producing photoelectric devices and atomic clocks. Since it ionises readily, it is used as an ion rocket motor propellant.

Electronic configuration: [Xe] 6s¹
Formal oxidation number: +1
Atomic radius: 265.5 pm

Electronegativities: 0.79
Thermal conductivity: 35.9 W/(m K)
Electrical resistivity (20 °C): 20 μΩcm

Melting point: 28.44 °C
Boiling point: 671 °C

Heat of fusion: 2.09 kJ/mol
Heat of vaporization: 66.5 kJ/mol
Heat of atomization: 77.58 kJ/mol