Classical Atomic Theory and Interatomic Binding

Abstract

Any theory of electrons in metals must account for the experimental observations on thermal and electrical conduction, photoelectric and thermionic emission, and on the specific heat of metals. Proof, that the particles emitted from metallic surfaces when illuminated by ultraviolet light or when heated to some 2,500°K were electrons, led to the suggestion that electrical conductivity in metals may be due to the existence of a cloud of free electrons in the interatomic spaces. The application of an electric field would then cause the electrons to move with the consequent production of a current, the flow of electrons being in the opposite direction to that of the conventional current. This theory, known as the classical theory, was developed by Drude and Lorentz. They assumed that the electrons, when accelerated by an electric field, collided with each other and with the atomic nuclei, and had the usual Maxwellian distribution of velocities, see section 3.5, appropriate to the temperature of the metal. They also showed that these free electrons would account for the high thermal conductivity of metals, because as their masses were considerably less than those of the atoms, they would have correspondingly high velocities.