Energy bands and band gaps in materials
Isolated atoms have energy levels corresponding to s, p, d, f orbitals etc. However, as we bring atoms close together we have to worry about overlap leading to multiple electrons having the same quantum numbers. This would violate pauli exclusion principle!! Instead, we have to slightly change energy levels to form energy bands. These bands an also have band gaps which are regions of energy where no electrons are allowed to occupy (no seats!) These bands can explain electrical conductivity of metals, semiconductors, and insulators.
Copyright image attribution:
https://en.wikipedia.org/wiki/Band_ga...
https://en.wikipedia.org/wiki/Valence...
File:Semiconductor band structure (lots of bands).png: Tim Starling vectorisation: Mliu92 - file:Semiconductor band structure (lots of bands).png
CC BY-SA 4.0
File:Semiconductor band structure (lots of bands 2).svg
Created: 7 April 2015