The decreasing order of stability of ${\mathrm{O}}_2,{\mathrm{O}}_2^{-},{\mathrm{O}}_2^{+}$ $\mathrm{and}$ ${\mathrm{O}}_2^{2-}$is: 

1. ${\mathrm{O}}_2^{+}>{\mathrm{O}}_2>{\mathrm{O}}_2^{-}>{\mathrm{O}}_2^{2-}$

2. ${\mathrm{O}}_2^{2-}>{\mathrm{O}}_2^{-}>{\mathrm{O}}_2>{\mathrm{O}}_2^{+}$

3. ${\mathrm{O}}_2>{\mathrm{O}}_2^{+}>{\mathrm{O}}_2^{2-}>{\mathrm{O}}_2^{-}$

4. ${\mathrm{O}}_2^{-}>{\mathrm{O}}_2^{2-}>{\mathrm{O}}_2^{+}>{\mathrm{O}}_2$

Which of the following species contains an equal number of $\mathrm{\sigma }$ and $\mathrm{\pi }$ bonds?

1. ${\mathrm{HCO}}_3^{-}$

2. ${\mathrm{XeO}}_4$

3. ${\left(\mathrm{CN}\right)}_2$

4. CH₂(CN)₂

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

Choose the compound which has a maximum bond angle at nitrogen among the following:
1. ${\mathrm{NO}}_2$
2. ${{\mathrm{NO}}_2}^{-}$
3. ${{\mathrm{NO}}_2}^{+}$
4. ${{\mathrm{NO}}_3}^{-}$

The correct order of bond order in the following species is:

A molecule among the following that has the maximum dipole moment is:

Which one of the following species has a plane triangular shape?

An electron-deficient compound among the following is: