JEE Main 2026 Apr 6 Shift 1, Chemistry Q4: Important Concepts Of Chemical Bonding

Compare the two species in each pair by counting valence electrons and shape:

A: ${\text{SO}}_3^{2-}$ is pyramidal (S has a lone pair) while ${\text{CO}}_3^{2-}$ is trigonal planar. Different Lewis structures.

B: ${\text{O}}_2^{2-}$ and ${\text{F}}_2$ are both isoelectronic ($18$ valence $e^{-}$), single bond, three lone pairs on each atom. Same.

C: ${\text{CN}}^{-}$ and $\text{CO}$ are isoelectronic ($10$ valence $e^{-}$), triple bond with one lone pair on each atom. Same.

D: ${\text{NH}}_3$ and ${\text{H}}_3{\text{O}}^{+}$ are isoelectronic, both pyramidal with one lone pair on the central atom. Same.

E: ${\text{MnO}}_4^{2-}$ has one unpaired $d$-electron on Mn ($d^1$), while ${\text{CrO}}_4^{2-}$ has no unpaired electrons ($d^0$). Different.

$\therefore$ A and E do not have similar Lewis dot structures.