Electron theory of metals

The most characteristics properties of metals are their high electrical and thermal conductivities.

For eg. :-The electrical conductivity at room temperature of silver is 0.6 X 10⁸ ohm^-1m^-1 as compare to  10^-16 for a good insulator and 2 X 10^-2 for a semiconductor such as germanium.

            The idea that the large electrical and thermal conductivity of metals might be explaind by the presence of mobile electrons (also called “free” or “conduction” electrons) in the metals was first put forward by Drude well before the introduction of quantum theory.

             Lorentz and Drude considered that about 95% of whole volume of solid is occupied by the electrons and 5% of the volume is occupied by ion core.hence according to free electron theory,the solids behaves as free electron gas.