Question

First ionisation enthalpy of Al is lower than that of Mg. this is because.

• A. The size of Al is bigger than Mg.
• B. Ionisation enthalpy decreases in a period from left to right
• C. It is easier to remove electon from unpaired $3p^{1}$ than from paired $3s^{2}$
• D. Aluminium is a passive metal while magnesium is active.

Answer 1

Answer: (C)

It is easier to remove electon from unpaired $3p^{1}$ than from paired $3s^{2}$

Answer 2

: Electronic configuration of $Al - 1s^{2}2s^{2}2p^{6}3s^{2}3p^{1}$

Electronic configuration of $Mg - 1s^{2}2s^{2}2p^{6}3s^{2}$

It is difficult to remove electron from paired $3s^{2}$- orbital than unpaired $3p^{1}$ Hence, I.E. of Al is lower than Mg.