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 electron from unpaired $3p^1$ than from paired $3s^2$
• D. aluminium is a passive metal while magnesium is active.

Answer 1

The Correct Option is C

Electronic configuration of \(${Al} - 1s^2 2s^2 2p^6 3s^2 3p^1$\) Electronic configuration of \(${Mg} - 1s^22s^22p^63s^2$\) It is difficult to remove electron from paired \($3s^2$\)-orbital than unpaired \($3p^1$\). Hence, \($I.E.$\) of \(${Al}$\) is lower than \(${Mg}$\).