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Question #44310

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The Question

Consider the diagonal relationship between Beryllium (Period 2) and Aluminum (Period 3), which manifests in the amphoteric nature of their oxides, \ce{BeO} and \ce{Al2O3}. Both oxides dissolve completely in excess aqueous \ce{NaOH} at 298 K to form mononuclear hydroxo-complexes $X$ and $Y$ respectively. Which of the following statements correctly describes the hybridization of the central metal in $X$ and $Y$ , and the fundamental atomic phenomenon responsible for their identical acid-base behavior?

Options

A.
Both $X$ and $Y$ are $sp^3$ hybridized. The identical acid-base behavior is due to their similar ionic potentials ( $\phi = z/r$ ), where the $+9$ increase in nuclear charge from \ce{Be} to \ce{Al} is imperfectly shielded by the additional inner shell electrons, contracting the \ce{Al^{3+}} radius to compensate for the higher principal quantum number.
B.
$X$ is $sp^3$ and $Y$ is $sp^3d^2$ hybridized. The identical acid-base behavior is due to the identical effective nuclear charge ( $Z_{eff}$ ) experienced by the valence electrons of \ce{Be} and \ce{Al}, caused by the perfect shielding of the $2p^6$ subshell in \ce{Al}.
C.
Both $X$ and $Y$ are $sp^3$ hybridized. The identical acid-base behavior is due to the identical first ionization enthalpies of \ce{Be} and \ce{Al}, resulting from the penetration effect of the $3s$ orbital in \ce{Al} overcoming the screening of the inner shells.
D.
$X$ is $sp^2$ and $Y$ is $sp^3d^2$ hybridized. The amphoteric nature is a consequence of the diagonal relationship, which dictates that elements with identical screening constants ( $\sigma$ ) form oxides with identical lattice enthalpies.

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How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Diagonal Relationship|Acid-Base Nature of Oxides|Screening Effect in Inner Shells

Why This Question Is Tricky

Common Mistakes

The question tests the fundamental atomic reason behind the diagonal relationship, moving beyond the superficial 'similar size/electronegativity' memorization.

It targets the 'Screening Effect' trap: students often fail to realize that the contraction of the \ce{Al^{3+}} radius (which maintains the high ionic potential required for amphoterism) is driven by the imperfect mutual shielding of the inner shell electrons against a massive $+9$ increase in nuclear charge.

Furthermore, it tests coordination chemistry knowledge by trapping students who assume \ce{Al} will automatically expand its octet to form $sp^3d^2$ \ce{[Al(OH)6]^{3-}} in standard aqueous \ce{NaOH}, whereas the major species is the tetrahedral $sp^3$ \ce{[Al(OH)4]^{-}}.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Classification of Elements and Periodicity in Properties - Class 11 Part 1
Concept	Diagonal Relationship
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free