Question

Explain the bond formation between, ${\mathrm{NH}}_3$ and ${\mathrm{CH}}_4$ (VBT)?

Answer 1

Valence Bond Theory

• The valence bond theory describes the occupation of electrons of a molecule in an atomic orbital rather than a molecular orbital.
• It describes the bonding between the molecules. According to VBT, the overlap of two incomplete-filled orbitals forms a chemical bond.

Bond formation in Methane

• The tetrahedral geometry in Methane molecule is the ${\mathrm{sp}}^3$ hybridization.
• The mixing of one $2\mathrm{s}$ and three $2\mathrm{p}$ orbitals gives rise to ${\mathrm{sp}}^3$ hybridization.

• The electrons occupy the orbitals according to Hund's rule and carbon has four filled orbitals and bonds with four hydrogen atoms.

Bond formation of Ammonia

• On the other hand, the Ammonia molecule has $s{p}^3$ with one lone pair.
• The lone pair present lowers the bond angle and is equal to ${107}^{°}$.

• So the bond formation in Ammonia and Methane is according to the VBT rules concerning ${\mathrm{sp}}^3$ hybridization.