During change of $O_2$ to $O_2^{-}$ ion, the electron adds in which one of the following orbitals? $$

1.  $\pi$ $\mathrm{orbital}$ $$

2.  $\sigma *$ $\mathrm{orbital}$ $$

3.  $\sigma$ $\mathrm{orbital}$

4.  $\pi *$ $\mathrm{orbital}$ $$

Four diatomic species are listed below. Identify the correct order in which the bond order is increasing in them.
1. O₂^– < NO < C₂^2– < He₂⁺  
2. C₂^2– < He₂⁺ < O₂^– < NO  
3. He₂⁺ < O₂^– < NO < C₂^2–
4. NO < O₂^– < C₂^2– < He₂⁺  

The pairs of species of oxygen and their magnetic behaviours are given below. Which of the following represents the correct description?

1. $\mathrm{O},$ ${\mathrm{O}}_2^{2-}$ - Both paramagnetic
2. ${\mathrm{O}}_2^{-},$ ${\mathrm{O}}_2^{2-}$ - Both diamagnetic
3. ${\mathrm{O}}^{+},$ ${\mathrm{O}}_2^{2-}$ - Both paramagnetic
4. ${\mathrm{O}}_2^{+},$ ${\mathrm{O}}_2$ - Both paramagnetic

Some of the properties of the two species, $N{O}_3^{-}$ $and$ $H_3{O}^{+}$  are described below. Which one of them is correct?
 

The most preferred structure among the following with the lowest energy for SO₃ is: 

1.		2.
3.		4.

Among the following, the compound that is electron deficient is:

1. BaCl₂

2. BCl₃

3. CCl₄

4. PCl₅

d$\mathrm{\pi }$ - p$\mathrm{\pi }$ bond is present in:

1. $C{O}_3^{2-}$

2. $P{O}_4^{-3}$

3. $N{O}_3^{-}$

4. $N{O}_2^{-}$

The compound that forms linear polymer due to H-bond is:

The correct order of dissociation energy of N₂ and N₂⁺ is:

Among the options given below, identify the Isoelectronic species:

1. CO, CN^–, NO⁺, C₂^2–

2. CO^–, CN, NO, C₂^–

3. CO⁺, CN⁺, NO^–, C₂

4. CO, CN, NO, C₂