Electron binding energy

The electron binding energy is the minimum energy that is required to remove an electron from an atom, as the negatively charged electrons are held in place by the electrostatic pull of the positively charged nucleus. The electron binding energy is measured in electron volt (eV), where 1 eV = 1.6 x 10J.

The magnitude of the electron binding energy is:

• directly proportional to the atomic number (Z)
• inversely proportional to the distance from the nucleus, i.e. inner-shell electrons will have greater binding energy than outer-shell electrons

An electron can only be removed from an atom if the applied energy is greater than its electron binding energy. When an inner-shell electron is ejected, the vacancy will be filled by an electron from an outer shell. The excess energy from this shift is emitted as electromagnetic radiation.