In solids, electron energy levels are so close together that they form almost-co

Question

In solids, electron energy levels are so close together that they form almost-continuous bands. Electrons bound into atoms are in the so-called valence band. Above that in energy is a so-called conduction band. Electrons that happen to be in the conduction band can travel throughout the solid... colliding with atoms on the way. In terms of that physical situation, how do materials that are conductors differ from materials that are insulators?

1. In an insulator the electrons are shielded from outside influences, while in a conductor they are sensitive to the slightest changes.

2. In an insulator there is a large energy gap between the top of the valence band and the bottom of the conduction band, while in a conductor the two bands actually overlap... there is no gap.

3. In an insulator the conduction band does not exist.

4. In conductors the electrons almost never collide with atoms, whereas in insulators they run into atoms all the time.

5. In conductors atoms have many more electrons, compared to the atoms in insulators.

6. In conductors atoms collide so often that electrons are often knocked up into the conduction band, whereas in insulators, atoms never collide at all

Explanation / Answer

In these case Option (2) is correct.

The typical gap between valence band and conduction band in insulators like Diamond is of the order of 7eV.In conductors this gap is almost absent because the bands overlap.

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