APPLICATION OF VALENCE BOND THEORY

Many different approaches have been proposed in order to understand the nature of bonding in coordination molecules. The Valence Bond (VB) Theory is one of these theories. To better understand chemical bonding, the Valence Bond Theory was established, which uses the method of quantum mechanics to do so. Individual bonds are formed during the construction of a molecule predominantly through the interaction of the atomic orbitals of the participating atoms, according to the principles of this theory.

A covalent bond is defined by valence bond theory as the intersection of two half-filled atomic orbitals (each carrying a single electron) that results in the sharing of two electrons between the two bound atoms. When a portion of one orbital and a portion of another orbital occupy the same region of space on two separate atoms, we say that they overlap. Covalent bonds arise when two requirements are met:

• an orbital on one atom overlaps an orbital on another atom, and 
• The solitary electrons in each orbital unite to create an electron pair. 

The attraction between this negatively charged electron pair and the positively charged nuclei of the two atoms serves to physically connect the two atoms via a force called a covalent bond. The strength of a covalent bond is determined by the amount to which the orbitals involved overlap. Orbitals with a high degree of overlap establish stronger links than those with a low degree of overlap.

Single bonds have a single sigma bond, double bonds have a sigma bond and a pi bond, and triple bonds have a sigma bond and two pi bonds. However, the bonding atomic orbitals may be hybrids. Often, the bonding atomic orbitals exhibit characteristics of numerous different orbital types. Hybridization is the process of obtaining an atomic orbital with the proper character for bonding.

History

The Lewis approach to chemical bonding was unable to give insight on how chemical bonds are formed. Additionally, the notion of valence shell electron pair repulsion (or VSEPR theory) had a limited use (and also failed in predicting the geometry corresponding to complex molecules).

To solve these challenges, German physicists Walter Heinrich Heitler and Fritz Wolfgang London proposed the valence bond hypothesis. The Schrodinger wave equation was also used to explain how two hydrogen atoms form a covalent connection. The chemical bonding of two hydrogen atoms is illustrated here using the valence bond theory.

This theory is concerned with the notions of electronic configuration, atomic orbitals (and their overlapping), and atomic orbital hybridization. Chemical bonds are established by the overlapping of atomic orbitals within which the electrons are confined.

Additionally, the valence bond theory explains the electrical structure of the molecules created by this overlapping of atomic orbitals. Additionally, it underlines how one atom’s nucleus is attracted to the electrons of the other atoms in a molecule.

Valence Bond Theory’s Application

The requirement of a maximum intersection is an important component of the Valence Bond theory, since it hints at the establishment of the strongest conceivable bonds. This idea is used to describe the formation of covalent bonds in a wide variety of compounds.

For example, in the case of the F2 particle, the F-F bond is formed by the intersection of the two F atoms’ pz orbitals, each of which contains an unpaired electron. Following that, the natures of the intersecting orbitals in H2 hydrogen and F2 fluorine molecules are different, as are the bond strengths and bond lengths between H2 and F2 molecules.

The covalent bond in an HF molecule is formed by the intersection of the 1s orbital of hydrogen and the 2pz orbital of fluorine, each of which contains an unpaired electron. The fact that H and F share electrons results in a covalent link in HF.

Conclusion

 The Valence bond hypothesis is significant because it aids in the comprehension of the concept of molecule bonding. This article discussed the VBT postulates, their application, and contemporary VBT.

It is vital to note that the need of a maximum intersection is a crucial component of the Valence Bond theory, since it implies the construction of the strongest potential links. A vast variety of compounds are described by this concept, which is used to describe the creation of covalent bonds.