Question

If two molecular orbitals are orthogonal, their net overlap is 0, which means that the mixture of them would result in no observable change in any of the orbitals if they occur. However, this contrasts totally with the Molecular Orbital Theory as well as the Valence Bond Theory, whereby atomic orbitals are often combined. In this manner, is it not plausible that the orthogonality condition of the wave function hinders the combination of orthogonal wave functions i.e. atomic orbitals?

Answer 1

Molecular Orbital Theory and Valence Bond Theory allow for the combination of atomic orbitals through constructive and destructive interference. The linear combination of atomic orbitals can lead to bonding and antibonding molecular orbitals, while hybridization in Valence Bond Theory explains molecular geometries such as the tetrahedral arrangement in water molecules.

Step-by-step explanation:

The concern that the orthogonality condition of wave functions might hinder the combination of atomic orbitals is addressed within Molecular Orbital (MO) Theory and Valence Bond Theory.

Despite the orthogonal nature of some wave functions, which have a net overlap of zero, MO Theory and Valence Bond Theory still allow atomic orbitals to combine by taking advantage of constructive and destructive interference.

On a molecular level, the linear combination of atomic orbitals (LCAO) allows atomic wave functions to combine, creating new molecular orbitals.

These combinations can lead to bonding molecular orbitals when the wave functions interfere constructively, with regions of higher electron probability, or antibonding orbitals, when they interfere destructively, leading to nodes or regions of no electron density.

Valence Bond Theory further complicates this picture by introducing the concept of hybridization, which explains the geometry and bonding in molecules like H2O, where hybrid orbitals are formed from the LCAO process, creating geometries such as the tetrahedral arrangement in water based on sp3 hybridization.