Bands

Clicking a thumbnail on this web page (http://chemistry.beloit.edu/edetc/cineplex/bands/index.html) shows a movie of that demonstration.

The band gap is the energy difference between the valence band and the conduction band. The dark shading represents electrons in the band. Insulators have a large band gap, and metals have a small band gap. Semiconductors are the intermediate case.

Applying a voltage to a metal tips the bands, resulting in a flow of electrons.

When electrons from the conduction band recombine with holes from the valence band, the energy released is in the form of light.

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