JEE Main 2026 — Apr 4, Shift 2 — Chemistry solution

JEE Main2026Apr 4, Shift 2Chemistry

Consider the metal complexes [Ni(en) $_{3}$ ] $^{2 +}$ (A), [NiCl $_{4}$ ] $^{2 -}$ (B) and [Ni(NH $_{3}$ ) $_{6}$ ] $^{2 +}$ (C). Choose the CORRECT option by considering the number of unpaired electron present in (A), (B) and (C) respectively and the order of frequency of absorption.

A
2, 2, 2 and (A) $>$ (C) $>$ (B)
B
0, 2, 0 and (A) $>$ (C) $>$ (B)
C
2, 2, 0 and (B) $>$ (C) $>$ (A)
D
2, 2, 2 and (C) $>$ (A) $>$ (B)

Solution

Ni $^{2 +}$ is d $^{8}$ in every case.

(A) [Ni(en) $_{3}$ ] $^{2 +}$ : octahedral, en is strong field but for d $^{8}$ octahedral the $t_{2 g}^{6} e_{g}^{2}$ filling is forced — 2 unpaired.

(B) [NiCl $_{4}$ ] $^{2 -}$ : tetrahedral, $e^{4} t_{2}^{4}$ — 2 unpaired.

(C) [Ni(NH $_{3}$ ) $_{6}$ ] $^{2 +}$ : octahedral d $^{8}$ , $t_{2 g}^{6} e_{g}^{2}$ — 2 unpaired.

Crystal field splitting / absorption frequency: $Δ_{o} > Δ_{t}$ for the same ligand, and ligand field strength order here is en $>$ NH $_{3}$ $≫$ Cl $^{-}$ . So absorption frequency follows the same trend:

(A) $>$ (C) $>$ (B).

$∴$ 2, 2, 2 and (A) $>$ (C) $>$ (B).

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