Question

Q12. Explain the formation of energy bands in solids.Draw energy band
diagram for (i) Conductor (ii) semiconductor (iii) insulator.
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Answer 1

The band theory of solids is different from the others because the atoms are arranged very close to each other such that the energy levels of the outermost orbital electrons are affected. But the energy level of the innermost electrons is not affected by the neighbouring atoms. The three energy bands in solids are

Valence band

Conduction band

Forbidden band

Bond theory solids

In atoms, electrons are filled in respective energy orbits following Pauli’s exclusion principle.

In molecules, Two atomic orbitals combine together to form a molecular orbit with two distinct energy levels.

In solids, 1023 stacked up lines confined in a tiny space would look like a band. Thereby forming energy continuum called energy bands.

This theory helps to visualise the difference between conductor, semiconductors and insulator by plotting available energies for an electron in a material.

Answer 2

see the attached and scroll it