Chapter 2: Electronic Structure of Atoms

2.1. Introduction

In this Chapter the electronic structure of single atoms will be discussed. A few quantum concepts will be introduced, as they are necessary for the understanding of many aspects in solid state physics and device applications.

In Chapter 1, we saw that matter was composed of atoms in the periodic table shown in Fig. 1.2. Until 1911, atoms were considered the simplest constituents of matter. In 1911, it was discovered that atoms had a structure of their own and Rutherford proposed the nuclear model of the atom in which almost all the mass of the atom is concentrated in a positively charged nucleus and a number of negatively charged electrons are spread around the nucleus. It was later found that the nucleus is itself made up of protons (positively charged) and neutrons (neutrally charged). The number of protons is the atomic number (Z) while the total number of protons and neutrons is the mass number of the element. Apart from the electrostatic repulsion between nuclei, all of the major interactions between atoms in normal chemical reactions (or in the structures of elemental and compound substances) involve electrons. It is therefore necessary to understand the electronic structure of atoms. The term electronic structure, (or configuration) when used with respect to an atom, refers to the number and the distribution of electrons about the central nucleus.

The following discussion traces the steps of the scientific community toward a description of the electronic structure of atoms. The reader should not be...