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Explain the formation of energy bands in solids. On the basis of energy bands distinguish Vetween a metal, a semiconductor and an insulator. |
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Answer» Solution :Formation of energy bands : In an isolated (free) atom, the energy levels of ELECTRONS are WELL defined. In SOLIDS, nucleus of each atom INTERACTS with the electrons of the neighbouring atoms. Also valence electrons of different neighbouring atoms interacts with each other. Due to this, energy levels are slightly altered. These different energy levels with continuous variation are called energy bands, Mainly there are two types of energy bands. They are valence band(VB) and conduction band(CB). The gap between the top of VB and bottom of CB is the energy band gap `(E_g)` . 
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