CHAPTER 3 - Chemical Bonding

Abstract

This chapter focuses on the process of chemical bonding. The simplest type of bonding occurs between unpaired electrons, that is, electrons which occupy an atomic orbital alone. If two atoms A and B each have an unpaired electron, these two electrons can enter a new orbital and form a bond. The new orbital is some composite of the atomic orbitals and its wave function is a mathematical combination of the wave functions of the atomic orbitals. The simplest of all bonds is the bond formed between two atoms of hydrogen. Each atom has one unpaired electron in the 1s orbital. These leave the atomic 1s orbitals and enter a new orbital. The two electrons in the new orbital hold the two nuclei together. The distance between the nuclei is that which gives the greatest energy reduction. The closer the nuclei, the greater is the overlap of the two atomic orbitals, and the lower the energy level of the new orbital. At small separations, this is offset by the repulsion between the two nuclei. There would be some separation, which gives a minimum potential energy. In some cases, the difference in electronegativity value is so large that the charge separation is virtually complete. This results from the two electrons involved in the formation of the bond being in the atomic orbitals of one of the atoms. The most simple example of this type of bonding occurs between an atom of fluorine and an atom of lithium.