Given below are two statements

Statement-I: The correct order for radius is Al > Mg > Mg2+ > Al3+

Statement-II: Atomic size always, depends on electronegativity.

In the light of the above statements, choose the correct option.

The correct option is: Both Statement-I and II are incorrect.

Let us analyze both statements step-by-step to understand why they are incorrect:

Analysis of Statement-I:

Statement-I gives the order of radius as: Al > Mg > Mg²⁺ > Al³⁺.

1. Across a period from left to right (from Mg to Al), the nuclear charge increases while electrons are added to the same energy shell. Thus, effective nuclear charge increases, which causes atomic size to decrease. Therefore, the atomic radius of Mg is greater than Al (Mg > Al).

2. For isoelectronic species (Mg²⁺ and Al³⁺, both having 10 electrons):

Mg²⁺ has 12 protons, whereas Al³⁺ has 13 protons. Higher effective nuclear charge in Al³⁺ pulls the electrons closer, making its ionic radius smaller than that of Mg²⁺. Thus, Mg²⁺ > Al³⁺.

3. Furthermore, neutral atoms are always larger than their corresponding cations (Mg > Mg²⁺ and Al > Al³⁺).

Comparing the actual atomic and ionic radii (in pm):

Atomic radius of Mg ≈ 160 pm

Atomic radius of Al ≈ 143 pm

Ionic radius of Mg²⁺ ≈ 72 pm

Ionic radius of Al³⁺ ≈ 53.5 pm

Therefore, the correct decreasing order of radius is:

$\text{Mg}>\text{Al}>{\text{Mg}}^{2+}>{\text{Al}}^{3+}$

Since Statement-I claims Al > Mg, Statement-I is incorrect.

Analysis of Statement-II:

Statement-II claims that atomic size always depends on electronegativity.

Atomic size primarily depends on factors such as principal quantum number (number of electron shells) and effective nuclear charge ($Z_{\text{eff}}$). Electronegativity is actually a property that is influenced by atomic size and effective nuclear charge, not the primary fundamental driver determining atomic size. Moreover, absolute statements using terms like "always" are incorrect in chemical trends (for instance, noble gases have high atomic radii due to van der Waals radii definition regardless of electronegativity). Therefore, Statement-II is incorrect.

Conclusion: Both Statement-I and Statement-II are incorrect.