In what type of material is the energy gap between the valence band and the conduction band greatest: metal, semiconductor, or insulator? Explain.

Short Answer

Expert verified
The energy gap between the valence band and the conduction band is greatest in an insulator.

Step by step solution

01

Understanding Band Theory

Band theory describes how electrons inhabit energy bands, and in a material, there are two main bands: the valence band, which is the band containing the highest energy electrons that are involved in bonding of the material, and the conduction band, which is higher in energy and usually empty. The gap between these two bands is known as the band gap.
02

Identifying Band Gaps in different materials

In metals, this band gap is non-existent or very small, meaning that electrons can move freely between the valence and conduction bands, which allows metals to conduct electricity. Semiconductors have a moderate band gap, and when this band gap is overcome (often by heat), they can conduct electricity. Insulators, on the other hand, have a large band gap, which prevents electrons from moving to the conduction band, making them poor conductors of electricity.
03

Conclusion

Therefore, based on the properties and definition of the band theory, the energy gap between the valence band and the conduction band is greatest in an insulator.

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