Conduction of Electricity in Metals
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A conductor conducts electricity due to the movement of electrons or ions.
o Metals conduct electricity both in solid state as well as molten state.
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The conductivity of metals depends upon the number of valence electrons available per atom.
The atomic orbitals of metal atoms form molecular orbitals that are close in energy to each other as to form a band.
Partial filling or overlapping with a higher energy unoccupied conduction band enables the electrons to flow easily under an applied electric field.
o This results in conductivity of metals.
If the gap between valence band and the conduction band is large, electrons cannot jump to it and such a substance has very low conductivity that makes it behave like an insulator
Conduction of Electricity in Semiconductors
In semiconductors, the gap between the valence band and conduction band is small.
This enables some electrons to jump to conduction band and exhibit their conductivity.
Electrical conductivity of semiconductors increases with increase in temperature, since more electrons can jump to the conduction band due to small gap between the valence band and conduction band.