Explanation:
A covalent bond is formed by the overlap of half filled atomic orbitals of different atoms. Overlapping atomic orbitals must have electrons with opposite spins. The bonded electron pair is localized between two linked atoms. The stability of covalent bond is due to exchange of valence electrons between participation atoms, which lowers potential energy of the bonded atoms. Each atom of the compound attains a noble gas configuration.
This is for the advanced class
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