Which elements are generally used in the ‘Atomic clocks?

An international group has proposed a lunar time standard to address time discrepancies on the Moon due to its unique gravity. Atomic clocks, crucial for precision in GPS, telecom, and research, are the most accurate timekeeping devices. These clocks measure time using the stable resonant frequencies of atoms like cesium-133. One second is defined by the vibration of a cesium atom 9,192,631,770 times. Atomic clocks work by introducing a microwave signal to cesium atoms, detecting emitted radiation, and adjusting timekeeping for continuous precision.