all the MOs are populated in the ground state, electrons can
move into vacant MOs within the band under the influence of
an electric field. Because of the delocalization, we can readily
rationalize the movement of electrons from one Li atom
to another, and understand why electrical conductivity
results. This model indicates that electrical conductivity is
a characteristic property of partially filled bands of MOs.
In theory, no resistance should oppose the flow of a current
if the nuclei are arranged at the points of a perfectly ordered
lattice, and the increased thermal population of higher energy
levels within the band at higher temperatures might be
expected to lead to an increase in the electrical conductivity.
In practice, however, thermal vibrations of the nuclei
produce electrical resistance and this effect is sufficiently
enhanced at higher temperatures so as to result in a decrease
in the conductivity of the metal as the temperature increases