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 decrease in a period from left to right
• C. it is easier to remove an electron from unpaired $3p^1$ than from paired $3s^2$
• D. aluminium is a passive metal while magnesium is active metal

Answer 1

Answer: (C)

it is easier to remove an electron from unpaired $3p^1$ than from paired $3s^2$

Answer:- (C) it is easier to remove electron from unpaired $3p^1$ than from paired $3s^2$.

Reason:-

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

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

Al has one unpaired electron in it's highest energy orbital (3p), and Mg's highest energy orbital (3s) has the paired electrons.

It is energetically favourable for all the electrons in an orbital to be paired, which means that breaking up this pair would require more energy.