Discuss the orbtial concept or quantum concept for the formation of covalent bond.
Or
Explain the formation of covalent bond on the basis of valence bond theory.

According to the orbital concept, a covalent bond is formed by the partial overlap of two half-filled atomic orbitals containing electrons with opposite spins. During the orbital overlap, a certain amount of enthalpy is released. Greater the enthalpy released, stronger will be the bond formed. The new orbital which gets formed as a result of orbital overlap is called molecular orbital. For example, in the formation of H₂ molecule, orbital of each hydrogen atom having electrons in opposite spin overlaps mutually as shown.



This results in the formation of molecular orbital which contains both the electrons which now have got paired.