Chemistry - CHEMICAL BONDING Question with Solution | TestHub

Isoelectronic species have the same number of electrons.

A. ${\mathrm{PO}}_4^{-3}$ (50 e⁻), ${\mathrm{SO}}_4^{-2}$ (50 e⁻), ${\mathrm{ClO}}_4^{-}$ (50 e⁻) - Isoelectronic

B. ${\mathrm{CN}}^{-}$ (14 e⁻), ${\mathrm{N}}_2$ (14 e⁻), ${\mathrm{C}}_2^{2-}$ (14 e⁻) - Isoelectronic

C. ${\mathrm{SO}}_3^{-2}$ (42 e⁻), ${\mathrm{CO}}_3^{-2}$ (32 e⁻), ${\mathrm{NO}}_3^{-}$ (32 e⁻) - NOT Isoelectronic

D. ${\mathrm{BO}}_3^{-3}$ (32 e⁻), ${\mathrm{CO}}_3^{-2}$ (32 e⁻), ${\mathrm{NO}}_3^{-}$ (32 e⁻) - Isoelectronic

The correct answer is C because ${\mathrm{SO}}_3^{-2}$ has 42 electrons, while ${\mathrm{CO}}_3^{-2}$ and ${\mathrm{NO}}_3^{-}$ both have 32 electrons.