5.1 Introduction

As we have seen, an electron and a proton may strike up a companionship, the result being a hydrogen atom. We have found that the energy of the electron is a negative number, that is, the electron in the vicinity of the proton has a lower energy than it would have if it were an infinite distance away, which corresponds to zero energy. The minimum comes about as some sort of compromise between the kinetic and potential energy, but the important thing is that a minimum exists. The electron comes closer to find lower energy.

Can we say the same thing about two hydrogen atoms? Would they too come close to each other in order to reduce the total energy? Yes, they come close; they combine and make up a hydrogen molecule. This combination between atoms is called a chemical bond, and the discipline that is concerned with these combinations is chemistry.

You may justifiably ask why we talk of chemistry in a course on electrical properties of materials. Well, in a sense, chemistry is just a branch of the electrical properties of materials. The only way to explain chemical bonds is to use electrical and some specific quantum-mechanical properties. And not only is chemistry relegated to this position: metallurgy, is too. When a large number of atoms conglomerate and make...