Which of the following are isostructural pairs ? (A) $\mathrm{SO}_{4}^{2-}$ and $\mathrm{CrO}_{4}^{2-}$ (B) $\mathrm{SiCl}_{4}$ and $\mathrm{TiCl}_{4}$ (C) $\mathrm{NH}_{3}$ and $\mathrm{NO}_{3}^{-}$ (D) $\mathrm{BCl}_{3}$ and $\mathrm{BrCl}_{3}$

JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Chemical Bonding and Molecular Structure

Which of the following are isostructural pairs ?
(A)

SO_{4}^{2 -}

and

CrO_{4}^{2 -}

(B)

SiCl_{4}

and

TiCl_{4}

(C)

NH_{3}

and

NO_{3}^{-}

(D)

BCl_{3}

and

BrCl_{3}

Answer: (B)

Isostructural species have the same structure and geometry.

(A)

SO X_{4} X^{2 -}

and

CrO X_{4} X^{2 -}

: Both have 4 bonding pairs and 0 lone pairs on the central atom, giving them tetrahedral geometry. They are isostructural.

(B)

SiCl X_{4}

and

TiCl X_{4}

: Both are tetrahedral molecules with 4 bonding pairs and 0 lone pairs on the central atom. They are isostructural.

(C)

NH X_{3}

and

NO X_{3} X^{-}

NH X_{3}

has a trigonal pyramidal structure (3 bonding pairs, 1 lone pair), while

NO X_{3} X^{-}

has a trigonal planar structure (3 bonding pairs, 0 lone pairs). They are NOT isostructural.

(D)

BCl X_{3}

and

BrCl X_{3}

BCl X_{3}

is trigonal planar (3 bonding pairs, 0 lone pairs), while

BrCl X_{3}

is T-shaped (3 bonding pairs, 2 lone pairs). They are NOT isostructural.

Therefore, only pairs A and B are isostructural.

JEE Main · 2021 · 24 Feb 2021 · Shift 1 · Single correct option