Which orbital does the additional electron occupy when O₂ is converted to the O₂⁻ ion?

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

Which of the two species, NO₃⁻ or H₃O⁺, has the correctly described properties listed below?

In which of the following molecules the central atom does not have sp³ hybridization?

1. SF₄

2. $B{F}_4^{-}$

3. $N{H}_4^{+}$

4. CH₄

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

1.		2.
3.		4.