Question

Explain why metals are electrically conducting and ceramics are good insulators.

Answer 1

Electrical conductivity in metals is a result of the movement of electrically charged particles.The atoms of metal elements are characterized by the presence of valence electrons - electrons in the outer shell of an atom that are free to move about. It is these 'free electrons' that allow metals to conduct an electric current.

In other materials, such as ceramics, the molecules are held together by shared electrons that form strong covalent bonds. Since the electrons are tightly held, it requires a great deal of force to move them from one molecule to another, and that makes them insulators (non-conductors).Note that ceramics have some kind of conductivity, it's just extremely low. The conductivity of copper, for example, is ~6×107 S/m. Most ceramics have conductivities in the range of 10-3 S/m to 10-5 S/m. That's around 10 orders of magnitude less conductive than copper, but it is 10 orders of magnitude more conductive than air, for example (10-15 S/m).