Almost everything a person sees or touches in daily life, like the air we breathe, the food we eat, the clothes we wear, are the result of chemical bonds. The concept of chemical bonding lies at the very core of chemistry; it is what enables about little over one hundred elements to form millions of known chemical substances that make up our physical world.

After the Periodic Table and the concept of electron configuration were developed, scientists began to develop ideas about molecules and compounds. In 1916, G.N. Lewis concluded that atoms combine in order to achieve a more stable electron configuration resulting in molecules or compounds.

As independent particles, atoms are at relatively high potential energy. Nature, favors arrangements in which potential energy is minimized. Most individual atoms exist in a less stable state than in their combined form.

In this chapter we will focus on three types of bonding, namely ionic bonding, covalent bonding and metallic bonding.

Octet Rule

You have studied in chapter 4 that noble gases have very stable electron arrangements such as 2; 2, 8; 2, 8, 8 and their outer shells are fully saturated. The first three are shown in and explains why noble gases are so reluctant to form compounds with other elements.

The noble gases have very stable electronic configuration, as reflected by their high ionization energies, low electron affinity and general lack of reactivity. Because all noble gases (except He) have eight valence electrons, many atoms undergoing reaction also attain eight valence electrons. The ns²np⁶ electronic configuration of the valence shell of all noble gas (except Helium) atoms, is commonly called an octet of electrons. The octet rule, a useful generalization that applies to all types of bonding which states that when atoms bond, they lose, gain or share electrons to attain the electronic configuration ns²np⁶ of the nearest noble gas. Nearly every main-group monoatomic ion has a filled outer level of electrons (either two or eight), the same number as in the nearest noble gas.