Which of the following pairs of ions are isoelectronic and isostructural?

1. ${\mathrm{CO}}_3^{2-},$ ${\mathrm{SO}}_3^{2-}$

2. ${\mathrm{ClO}}_3^{-},$ ${\mathrm{CO}}_3^{2-}$

3. ${\mathrm{SO}}_3^{2-},$ ${\mathrm{NO}}_3^{-}$

4. ${\mathrm{ClO}}_3^{-},$ ${\mathrm{SO}}_3^{2-}$

An electron-deficient compound among the following is:

Identify the wrong statement among the following.