Question

Cu is good conductor of electricity on the basis of band theory

Answer 1

Metals' ability to conduct electric current comes from the proximity of the conduction and valence bands - insulators, or ineffective conductors of electricity, have a considerably greater gap between the bands, requiring more energy to move electrons to an area with a greater range of movement.

Answer 2

In metallic conductors such as copper or aluminum, the movable charged particles are electrons. ... According to band theory, a conductor is simply a material that has its valence band and conduction band overlapping, allowing electrons to flow through the material with minimal applied voltage.