Of the following sets, which one dose not contain isoelectronic species?

Number of electrons in ${\mathrm{SO}}_3^{2-}$= 16 + 8 * 3 + 2 = 42

Number of electrons in ${\mathrm{CO}}_3^{2-}$= 6 + 8 * 3 + 2 = 32

Number of electrons in ${\mathrm{NO}}_3^{-}$ = 7 + 8 * 3 + 1 = 32

These are not isoelectronic components because the quantity of electrons varies.

Hence, Option c is correct.