Valence Bond and Molecular Orbital: Two Powerful Theories that Nicely Complement One Another

Introductory chemistry textbooks often present valence bond (VB) theory as useful, but incorrect and inferior to molecular orbital (MO) theory, citing the electronic structure of O2and electron delocalization as evidence. Even texts that initially present the two theories on equal footing use language that biases students toward the MO approach. However, these “failures” of VB are really just misconceptions and/or misapplications of the theory. At their theoretical limits, both VB and MO are equivalent; they simply approach that limit from different sides. Certain concepts may be easier to grasp with one theory or the other so that having a commanding knowledge of both is extremely beneficial. However, presenting one theory as superior to the other suppresses the ability to look at a problem from both sides and is therefore detrimental to students and the whole of chemistry. It is time for VB and MO to be taught on equal footing like the complementary theories they are.