Talk:Conduction band

explain the difference of conductivity in semiconductor, conductor and insulator using energy diagram

Actually this is a very useful definition. I got to this through a link from another article which failed to clearly explain the role of the conduction band. Of course the description could be considerably more detailed. However, this does appear to be an important aspect of physics and at least as notable as the histories of minor suburban railway systems which go unchallenged elsewhere on Wikipedia. Persephone19 (talk) 21:54, 21 October 2011 (UTC)

Metals overlap bands? & Proposed deletion
The article, as it stands, says that metals have overlapping conduction and valence bands. This is not true in many classic metals. For example, let's look at the very best metal conductor there is: silver. As you can see in this site, the Fermi level in silver crosses only one band.

The usual definition of a metallic/semimetallic conductor, as far as I'm aware, is that the Fermi level crosses at least one band. This means that there are partially filled states which are able to transport charge from electrode to electrode.

I propose deleting this article and valence band, redirecting them to a fixed version of the band theory article.--Nanite (talk) 12:27, 11 May 2013 (UTC)

explanation in terms of free/bound and delocalised electrons is bogus
The description of "freeing" an electron from "its atom" is far off the mark. "Freeing" an electron is called ionization; conduction electrons are not free - they remain bound electrons, just like valence electrons. In one-particle theories of crystalline solids, energy levels are generally delocalized (they are Bloch waves), regardless whether valence or conduction band levels.

In a completely filled valence band, there are no vacant states, so the delocalized electrons cannot change to another state of similar energy (Pauli principle), i.e. no charge redistribution (= current) is possible. In contrast, the conduction band has empty states that are energetically degenerate (or near-degenerate), so electrons can change between these states easily (charge redistribution = current occurs). The differentiation into semiconductors, insulators and conductors/metals has therefore nothing to do with "free vs bound" or "localized vs delocalized" electrons, but is a a consequence of the Pauli principle and how the Fermi level lies relative to the bands.

Illustrations of overlapping valence and conduction bands are popular, but dubious (there is no meaningful way to differentiate which of the overlapping bands is the valence band and which is the conduction band). A consistent definition of valence/conduction bands is based purely on the energy relation of bands with respect to the Fermi level: conduction bands are the bands containing energy levels above the Fermi level; valence bands are bands containing the levels below the Fermi level. In a conductor, the valence and conduction bands are thus the same. — Preceding unsigned comment added by 27.96.110.66 (talk) 02:58, 30 September 2013 (UTC)