Metals are generally more conductive when they have fewer valence electrons. This is because the valence electrons in metals are loosely bound and are referred to as "free electrons" or "delocalized electrons." These free electrons can move easily throughout the metal's lattice structure, contributing to its high electrical conductivity.
When a metal has fewer valence electrons, there are fewer electrons available for bonding with neighboring atoms, and therefore, fewer electrons that are tightly held within the atomic structure. This leads to a greater number of free electrons that are available to move and carry electric current.
In metals, the valence electrons occupy the highest energy levels or energy bands called the "conduction bands." When an electric field is applied, the free electrons are accelerated by the electric potential and move through the lattice, effectively conducting electricity. The presence of more free electrons enhances the metal's ability to conduct electric current.
In contrast, nonmetals tend to have higher valence electron counts and do not possess free electrons to the same extent. Instead, the valence electrons in nonmetals are involved in covalent bonds, where they are localized between specific atoms and do not contribute to electrical conductivity.
It's worth noting that not all metals have the same conductivity, as factors such as crystal structure, impurities, and temperature can influence their conductivity. However, the number of valence electrons is a general indicator of the potential conductivity of a metal, with fewer valence electrons typically resulting in higher conductivity.