Molecular orbital-valence bond theory

Chapter 3. The Molecular Orbital-Valence Bond Theory of Excited States. 

Chapter 11. How to build Bridges by Molecular Orbital-Valence Bond Theory ... 

According to a qualitative discussion on N2H4 and N2P4 based on the so-called molecular orbital-valence bond theory, the N2P4 molecule tends to adopt the trans form rather than the gauche form (of N2H4) [39]. 

MOVE molecular orbital valence bond (quantum chemical theory)... 

Application of valence bond theory to more complex molecules usually proceeds by writing as many plausible Lewis structures as possible which correspond to the correct molecular connectivity. Valence bond theory assumes that the actual molecule is a hybrid of these canonical forms. A mathematical description of the molecule, the molecular wave function, is given by the sum of the products of the individual wave functions and weighting factors proportional to the contribution of the canonical forms to the overall structure. As a simple example, the hydrogen chloride molecule would be considered to be a hybrid of the limiting canonical forms H—Cl, H Cr, and H C1. The mathematical treatment of molecular structure in terms of valence bond theory can be expanded to encompass more complex molecules. However, as the number of atoms and electrons increases, the mathematical expression of the structure, the wave function, rapidly becomes complex. For this reason, qualitative concepts which arise from the valence bond treatment of simple molecules have been applied to larger molecules. The key ideas that are used to adapt the concepts of valence bond theory to complex molecules are hybridization and resonance. In this qualitative form, valence bond theory describes molecules in terms of orbitals which are mainly localized between two atoms. The shapes of these orbitals are assumed to be similar to those of orbitals described by more quantitative treatment of simpler molecules. 

MOLECULAR ORBITAL - VALENCE BOND (MOVB) THEORY... 

According to Molecular Orbital-Valence Bond (MOYB) theory, the vast majority... 

There are two major approaches to the calculation of molecular structure, valence bond theory (VB theory) and molecular orbital theory (MO theory). Almost all modern computational work makes use of MO theory, and we concentrate on that theory in this chapter. Valence bond theory, however, has left its imprint on the language of chemistry, and it is important to know the significance of terms that chemists use every day. The structure of this chapter is therefore as follows. First, we present VB theory and the terms it introduces. Next, we present in more detail the basic ideas of MO theory. Finally, we see how computational techniques based on MO theory pervade all current discussions of molecular structure, including the prediction of the physiological properties of therapeutic agents. 

Chemical Bonding 11 Molecular Shapes, Valence Bond Theory, and Molecular Orbital Theory... 

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