- In case of a single isolated atom, the electrons in any orbit possess definite energy. However, an atom in a solid is greatly influenced by the closely-packed neighbouring atoms. The result is that the electron in any orbit of such an atom can have a range of energies rather than a single energy. This is known as energy band. The range of energies possessed by an electron in a solid is known as energy band.
- The concept of energy band can be easily understood by referring to Fig. 1.8. Fig. (ii) shows the energy levels of a single isolated atom of silicon. Each orbit of an atom has a single energy.
- Therefore, an electron can have only single energy corresponding to the orbit in which it exists. However, when the atom is in a solid, the electron in any orbit can have a range of energies. For instance, electrons in the first orbit have slightly different energies because no two electrons in this orbit see exactly the same charge environment.
- Since there are millions of first orbit electrons, the slightly different energy levels form a band, called 1st energy band [See Fig. (iii)]. The electrons in the first orbit can have any energy range in this band. Similarly, second orbit electrons form second energy band and so on.
Wilfykil answered the question on
August 13, 2019 at 11:32