IE1 of sodium is lower than that of magnesium whereas IE2 of sodium is higher than that of magnesium. Noble gases have positive value of electron gain enthalpy.





Q.58:- Give reasons:
(i) IE1 of sodium is lower than that of magnesium whereas IE2 of sodium is higher than that of magnesium.
(ii) Noble gases have positive value of electron gain enthalpy.

 

Answer:-
(i) The effective nuclear charge of magnesium is higher than that of sodium. For these reasons, the energy required to remove an electron from magnesium is more than the energy required in sodium. Hence, the first ionization enthalpy of sodium is lower than that of magnesium.
However, the second ionization enthalpy of sodium is higher than that of magnesium.
This is because after losing an electron, sodium attains the stable noble gas configuration. On the other hand, magnesium, after losing on electron still has one electron.
(ii)Because of stable configuration.