Band gap theory|Hindi|Basic electronics engineering
Energy band:
In solid materials, the atoms are closedly packed, hence the atom's electrons overlap with each other. Due to this closedly packed atoms in solids, instead of single energy levels, there will be bands of energy levels formed. These set of energy levels, which are closely packed are called as Energy bands.
valance band:
The electrons that are present in the outermost shell are called as Valance Electrons.These valance electrons, containing a series of energy levels, form an energy band which is called as Valence Band.
Conduction Band:
at room temperature, few of the valence electrons leave the band to be free. These are called as free electrons. These free electrons are the ones which conduct the current in a conductor and hence called as Conduction Electrons. The band which contains conduction electrons is called as Conduction Band.
Forbidden energy gap:
The gap between valance and conduction band is called forbidden energy gap