Question

Which element is used as timekeeper in atomic clocks?

Answer 1

The principle of operation of an atomic clock is based on atomic physics. It uses the microwave signal that electrons in atoms emit when they change energy levels. An atomic clock uses an electron transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element.

Caesium-based atomic clocks use the electromagnetic transitions of caesium-133 atoms as a reference point. Caesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal.