How is orbital overlap maximum condition important for JEE exam calculations?

The concept of delocalization or resonance can be explained for quantum mechanical atomic models in which electrons are considered to be spread over the entire molecular orbital.

The fundamental assumption of the valence bond theory contradicts the delocalization. The valence bond theory assumes that a covalent bond forms from the overlap of atomic orbitals on adjacent atoms, and electron density is localized between two specific nuclei.

That is why VBT cannot explain energy stabilization due to the resonance property.

The central atom of nitrogen has 5 valence electrons as per the electronic configuraion. During the formation of ${\mathrm{N}\mathrm{H}}_3$ , 3 valence electrons forms three sigma bonds with hydrogen and one lone electron pair is left.

• The steric number  of the ammonia molecule: SN=3 bonds +1 lone pair $=4$ total electron domains.
• As per the steric number, there is ${\mathrm{s}\mathrm{p}}^3$ hybridisation in ammonia.
• The lone pair causes repulsion, which leads to a trigonal pyramidal geometry with bond angles of ${107}^{?}$ .