Class 11 NEET Chemistry Chemical Bonding And Molecular Structure Part 1

Step 1: Calculate the total number of electrons for each ion.For $\mathrm{CO}_3^{2-}$: $6$ (C) $+ 3 \times 8$ (O) $+ 2$ (charge) $= 32$ electrons.For $\mathrm{NO}_3^{-}$: $7$ (N) $+ 3 \times 8$ (O) $+ 1$ (charge) $= 32$ electrons.Since both have the same total number of electrons, they are isoelectronic.Step 2: Determine the structure of both ions.In $\mathrm{CO}_3^{2-}$, the central carbon atom is bonded to three oxygen atoms with no lone pair on carbon.In $\mathrm{NO}_3^{-}$, the central nitrogen atom is bonded to three oxygen atoms with no lone pair on nitrogen.Both have three bond pairs and zero lone pairs, so both adopt a trigonal planar geometry.Hence, they are isostructural.Step 3: Therefore, the pair $\mathrm{CO}_3^{2-}$ and $\mathrm{NO}_3^{-}$ is both isoelectronic and isostructural.Note: $\mathrm{ClO}_3^{-}$ and $\mathrm{SO}_3^{2-}$ are also isoelectronic (42 electrons each) and isostructural (both trigonal pyramidal), making the question technically ambiguous. However, the intended answer for this exam is $\mathrm{CO}_3^{2-}$ and $\mathrm{NO}_3^{-}$.