the band farthest from the nucleus has seven or eight electrons, which means it is mostly full. The electrons are therefore held in fixed positions. These contrasts translate into differences in how the materials conduct electric current, which might be thought of as a “flow” of electrons through a solid material. In a conductor, electrons move freely. In an insulator, they don’t. As the Bell Labs researchers would describe it, the electrons in an insulator essentially “act as a rigid cement” to bind together the atoms in the solid.
