Valence Bond Theory Definition:

A Valence Bond Theory is a theory used to describe the nature of atomic orbital overlap. According to this theory, a bond is treated as a sharing of electrons density between two atoms as a result of constructive interference.

Valence Bond Theory Explained:

Chemical bonds, as we know are formed when atoms share or give up (in case of ionic bonds) their valence electrons in order to attain the octet configuration. However, when gaining a deeper understanding of covalent bonds, the valence bond theory provides a simplistic approach to visualize the nature of the atomic orbital overlap. The theory explains that, during bond formation, the electron density/atomic orbitals of each atom overlaps or is shared with the other atom.

For Example – for a molecule of hydrogen we visualize the bond as the overlap of valence 1s orbital of each hydrogen atom. Similar goes for a molecule of oxygen on which case there is an overlap of the valence p orbital.

The bond theory thus helps us visualize all types of single, double and triple bonds occurring between all atoms. Also see sigma bonds, pi bonds