Question

Statement-I : The correct order of Ionization energy is $Na > Mg > Al > Ar$
Statement-II : Among the following elements $Sc, Ca$ and $Mg, Ca$ has highest $3^{rd}$ Ionisation Energy.

• (1) Both Statement I and Statement II are correct
• (2) Statement-I is correct but Statement-II is incorrect
• (3) Statement-I is incorrect but Statement-II is correct
• (4) Both Statement I and Statement II are incorrect

Answer 1

The Correct Option is D

Ionization Energy (IE) depends on atomic size, nuclear charge, and electronic configuration stability.
1. Evaluate Statement-I:
Across a period (Na to Ar), IE generally increases. Also, noble gases (Ar) have the highest IE. For $Na, Mg, Al$: $Mg ([Ne] 3s^2)$ has higher IE than $Al ([Ne] 3s^2 3p^1)$ because of the stable fully filled s-subshell. So order is $Ar > Mg > Al > Na$. Statement-I is incorrect.

2. Evaluate Statement-II:
• $Mg^{2+}$ has noble gas configuration ($[Ne]$). $3^{rd}$ IE involves removing $e^-$ from a stable core. Very high.
• $Ca^{2+}$ has noble gas configuration ($[Ar]$). $3^{rd}$ IE involves removing $e^-$ from a stable core. High, but less than Mg due to larger size.
• $Sc^{2+}$ is $[Ar] 3d^1$. $3^{rd}$ IE involves removing the last valence electron. Lowest of the three.
Thus, $Mg$ has the highest $3^{rd}$ IE. Statement-II is incorrect.

Conclusion: Both statements are incorrect. Option (4).