Covalent Bonding: Orbital Overlap and

HybridizationLecture 7

VSEPR is a simplification

and does not explain much.There is one more theory:

valence bond (VB)!

Key principleof the Valence Bond Theory:A covalent bond forms when the orbitals of two atoms overlap and the overlap region, which is between the nuclei, is occupied by a pair of electrons.The two wave functions are in phase so the amplitude increases between the nuclei.

Themes of the Valence Bond Theory:A set of overlapping orbitals has a maximum of two electrons that must have opposite spins.The greater the orbital overlap, the stronger (more stable) the bond.The valence atomic orbitals in a molecule are different from those in isolated atoms.There is a hybridization of atomic orbitals to form molecular orbitals.

Hybridization

is the process of orbital mixing.

It result in hybrid orbitals.

Key pointsabout hybridization:The number of hybrid (molecular) orbitals obtained equals the number of of atomic orbitals mixed.The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.

sp-Hybridization

sp2 -Hybridization

sp3 -Hybridization

sp-Hybridization

sp-Hybridization

sp-Hybridization

spd-Hybridization

Formation of -bond

Formation of -bond

- and - bonds in ethylene

- and -bonds

-(sigma) bond

-(pi) bond

THE END