Question

The first ionization enthalpy sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium. Why?

Answer 1

Because during second ionisation enthalpy electron is removed from stable electronic configuration state that is 2p6 so it will have high 2nd ionisation enthalpy than magnesium in which 2nd electron is removed from unstable electronic configuration state that is 3s1. Hope it will help you.