Question

Explain the formation of the following molecules using valence bond theory. 

a) N₂ molecule 

b) O₂ molecule 

(OR) 

Write the formation of double bond and triple bond according to valence bond theory. 

(OR) 

Who proposed Valence Bond Theory? Explain the formation of N₂ molecule by using this theory.

Answer 1

Linus Pauling was proposed valence bond theory. 

Formation of N₂ molecule :

1. Electronic configuration of Nitrogen is 1s² 2s² 2p_x¹ 2p_y¹ 2p_z¹. 

2. Suppose that p_x orbital of one Nitrogen atom overlaps the p_x orbital of other ‘N’ atom giving σ p_x – p_x bond along the inter nuclear axis. 

3. The p_y and p_z orbitals of one ‘N’ atom overlaps with the p_y and p_z orbital of other ‘N’ atom laterally giving π p_y – p_y and π p_z – p_z bonds. 

4. Therefore, N₂ molecule has a triple bond between two Nitrogen atoms.

Formation of O₂ molecule :

1. Electronic configuration of ‘O’ is 1s² 2s² 2p_x¹ 2p_y¹ 2p_z¹.

2. If the P_y orbital of one ‘O’ atom overlaps the p_y orbital of other ‘O’ atom along internuclear axis, a σ p_y – p_y bond is formed. 

3. p_z orbital of oxygen atom overlaps laterally, perpendicular to inter nuclear axis giving a π p_y – p_z bond.

4. So O₂ molecule has a double bond between the two oxygen atoms.