Electron binding energy is defined as the:

• A. Energy required to remove an electron from orbit
• B. Energy released through the process of ionization
• C. Energy of attraction between orbital electrons
• D. Energy of repulsion between protons in the nucleus

Answer: (A)

Electron binding energy is the energy needed to remove an electron from its bound state in an atom. This is the energy required to overcome the Coulomb attraction between the electron and the positively charged nucleus, i.e., to ionize the atom. That’s why the correct choice describes energy required to remove an electron from orbit. It isn’t the energy released during ionization, nor the energy of attraction between electrons, and it isn’t related to the repulsion between protons in the nucleus (which is nuclear binding energy). Binding energy varies by orbital, with inner-shell electrons having higher binding energies than outer-shell electrons.