Postulates Of Quantum Free electron Theory & Similarities

Quantum Free Electron Theory

Partial failure of classical free electron theory led Somerfield (1928) to propose the quantum free electron theory. He retained some of the assumptions of classical theory and introduced a few new assumptions. 

Assumptions of quantum free electron theory.

• The valence electrons are free to move about inside the metal.

• The potential inside the metal is constant.

• The force of attraction between the free electrons and the ionic core and the force of repulsion between electrons is negligible.

• The energies of electrons are quantized. The allowed discrete energy levels obey Pauli’s exclusion principle, according to which no two electrons can be in the same quantum state.

Similarities between Classical and Quantum Free Electron Theories:

• According to both the theories conduction is due to free electrons

• The attraction between electrons and positive ion cores and the repulsion between electrons themselves is neglected.

• The electrons are assumed to be confined to the metal by potential barriers at the boundaries and the potential inside the metal is assumed to be constant.