Molecular orbital theory is a model used to describe the electronic structure of molecules. It is based on the idea that the electrons in a molecule do not belong to specific atoms, but rather are delocalized throughout the entire molecule.
Molecular orbital theory takes into account the delocalization of electrons, while valence bond theory focuses on the overlap of atomic orbitals between atoms. Molecular orbital theory also allows for the formation of bonding and antibonding orbitals, while valence bond theory only considers the formation of bonds.
Bonding orbitals are formed when two atomic orbitals combine in-phase, resulting in an increase in electron density between the nuclei and a stabilizing effect. Antibonding orbitals are formed when two atomic orbitals combine out-of-phase, resulting in a decrease in electron density between the nuclei and a destabilizing effect.
The energy of a molecular orbital is determined by the overlap of the atomic orbitals and the number of electrons occupying the orbital. The more overlap and the more electrons, the lower the energy of the orbital.
Molecular orbital theory is important for understanding the electronic structure and properties of molecules. It allows for the prediction of bond order, bond length, and molecular stability. It also helps to explain the reactivity and chemical behavior of molecules.