Question

iv) second ionization energy of sodium is higher than that of second ionization energy of magnesium.

Answer 1

Sodium ( Na) have 11 electron and on heating it losses 1 electron i.e. its 1st ionization enthalpy and it aquire nobel gas electronic configuration . but in case of Mg it have 12 electron and on heating it losses 1 electron i.e its 1st ionization enthalpy and it losses 2nd electron easily as compared to Na.
Because Na after losing 1 electron aquire nobel gas electronic configuration so 2nd ionization enthalpy is higher than Mg.