Octet rule, definition

In 1923. Lewis published a classic book (later reprinted by Dover Publications) titled Valence and the Structure of Atoms and Molecules. Here, in Lewis s characteristically lucid style, we find many of the basic principles of covalent bonding discussed in this chapter. Included are electron-dot structures, the octet rule, and the concept of electronegativity. Here too is the Lewis definition of acids and bases (Chapter 15). That same year, Lewis published with Merle Randall a text called Thermodynamics and the Free Energy of Chemical Substances. Today, a revised edition of that text is still used in graduate courses in chemistry. 

The discussion above has indicated some of the limitations of the original Lewis/ Kossel descriptiOTi of chemical bonding and the manner in which it has been adapted to assimilate the multitude of new compounds being reported from chemical laboratories during the last century. Central to the model is the definition of the chemical bond as a pair of electrons and the adherence to the octet rule. 

As Moeller observed in the 1950s [106], Although the octet rule is definitely a useful concept, its applications are limited and it should not receive the universal attention normally focussed upon it. It is much more important that attention be directed to the important phenomenon of electron pairing. The concept that the electrons seek to pair with each other is nearly universal in application and is always useful as a first approximation in predicting chemical behaviour. This rule of two is far more fundamental than the rule of eight . To contemporary sensibilities, this seems a bit harsh and generally multicentred, and dative bonds which favour adherence to the octet rule represent a convenient starting point for discussion. 

Definitions. Define and illustrate the following terms (a) octet rule, (b) Lewis symbol, (c) ionic bond, (d) covalent bond, (e) crystal lattice energy, (f) Iree radical, (g) network covalent compound, (h) electronegativity, (i) polar molecule, (j) dipole moment, (k) formal charge, (1) oxidation number, (m) hydrogen bond, (n) dipole-dipole attraction, (o) London forces. 

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