Caesium

Article

Caesium is a soft, silvery-gold alkali metal with atomic number 55. It is highly reactive, melts near room temperature, and reacts vigorously with water to form caesium hydroxide and hydrogen.

Natural caesium consists mainly of the stable isotope caesium-133. Several radioactive isotopes are produced in nuclear fission, including caesium-137, which has been important in environmental monitoring and radiological safety.

The transition between two hyperfine energy levels in the ground state of caesium-133 defines the SI second. A second is the duration of 9,192,631,770 periods of the radiation associated with this transition.

Caesium atomic clocks provide exceptionally stable frequency standards used in navigation, telecommunications, metrology, and tests of fundamental physics. Caesium compounds also have specialised uses in drilling fluids, photoelectric devices, and scientific instruments.

Source details and credits

• Source / publisher: Wikipedia
• URL type: WWW
• Credits: Wikipedia
• URL: https://en.wikipedia.org/wiki/Caesium