Chapter U2.5, Problem 1E

Interpretation Introduction

Interpretation :

The reason due to which nitrogen bonds with hydrogen to form NH₃ but not NH₂or NH₄must be explained with the help of Lewis structure.

Concept Introduction :

Nitrogen is a p-block element of group 15 with 5 valence electrons.

Answer to Problem 1E

Nitrogen bonds with hydrogen to form NH₃ to acquire octet configuration which is a stable electronic configuration like noble gases.

Explanation of Solution

As per octet rule, all the atoms while bond formation try to attain octet electronic configuration. As there are already 5 valence electrons in N so in order to attain octet extra three electron are required which can be obtained by forming three single bonds with three hydrogen atom. So nitrogen bonds with three hydrogen to form NH₃ but not NH₂ or NH₄.

  

From the Lewis structure it is clear that nitrogen forms three single bonds with three hydrogen. There is one lone pair on nitrogen. Nitrogen has complete 8 electrons in the valence shell. If nitrogen bonds with two hydrogen atoms to form NH₂ then there will be three electrons remaining. Also, the octet will not be complete. If N bonds with four hydrogen atoms to form NH₄ then there will be positive charge on nitrogen atom which is also unstable.

Conclusion

Nitrogen bonds with three hydrogen to get stability.