The concepts surrounding the structure of the atom are fundamental requirements in the study of electronics. The outer shell of the Atom is referred to as the Valence shell.
When the atoms within a material have less than four valence electrons, those electrons can be easily broken free from their parent atom to form current. These materials are referred to as conductors. If a material is comprised of atoms with four valence electrons the material is categorized as a semiconductor. Materials with atoms that have more than four valence electrons are insulators.
Major Conductors in descending order
of conductivity