Core electrons Covalent bonding, theories

Hammett s view of the scope of the subject is summarized in the rarely mentioned sub-title of his book Reaction Rates, Equilibria, and Mechanisms . His conception of the subject still defines its core, but requires amplifying certain other topics are now usually deemed part of physical organic chemistry. Thus the rationalization of the experimental results of studies of reaction rates, equilibria, and mechanisms involves the application of the electronic theory of the structures and reactions of organic molecules, either in its early forms as developed by Robinson, Ingold, and others on the basis of the electron-pair covalent bond, or in its later forms involving quantum mechanical treatments. 

The electrons responsible for bonding are those in the outer shell, or valence shell, of an atom. Valence shell electrons are those that were not present in the preceding noble gas orbitals. We will focus attention on these electrons in our discussion of covalent bonding. The electrons in the lower energy nohle gas configuration are not directly involved in covalent bonding and are often referred to as core electrons. Lewis formulas show the number of valence shell electrons in a polyatomic molecule or ion (see Sections 7-5 through 7-9). We will write Lewis formulas for each molecule or polyatomic ion we discuss. The theories introduced in this chapter apply equally well to polyatomic molecules and to ions. 

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