The first ionization enthalpy of $\mathrm{Na}, \mathrm{Mg}$ and Si , respectively, are: 496,737 and $786 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The first ionization enthalpy $\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ of Al is:

JEE Main · 2022 · 29 Jul 2022 · Shift 1 · Classification of Elements and Periodicity

The first ionization enthalpy of

Na, Mg

and Si , respectively, are: 496,737 and

786 kJ mol^{- 1}

. The first ionization enthalpy

(kJ mol^{- 1})

of Al is:

Answer: (C)

Across period 3, ionization enthalpy generally increases:

Na < Al < Mg < Si

. Aluminum has a slightly lower IE than magnesium due to its

3 p^{1}

electron being easier to remove than one of magnesium's paired

3 s^{2}

electrons. Given

496 < IE (Al) < 737

, the value 577 kJ/mol fits this trend.

JEE Main · 2022 · 29 Jul 2022 · Shift 1 · Single correct option