Evolution and Development of Valence-Bond Theory

Valence-bond theory was formed on the basis of the classical ideas of valence bond. VB theory and molecular orbital(MO) Theory are the two most influential quantum-mechanical theories of chemical structure and nature of the chemical bond nowadays. VB theory has continued to develop over years. VB problems are resolved or are being solved. VB theory is a useful tool for chemical thinking. VB and MO theories play complementary and coordinate roles in explaining the nature of chemical bond. It is likely that the two theories will be made a unified version for use some day.