Answer to Question #14488 in Inorganic Chemistry for Anissa

Question #14488
How can we show that an element is conductive, insulating or semiconducting?
Some of them use "The Band theory" , what is it about?

Thank you.
Expert's answer
The Band Gap theory can explain this(It's not the same that Band theory.) Every
element has its own characteristic energy band structure. This variation in band
structure is responsible for the wide range of electrical characteristics
observed in various materials. In semiconductors and insulators, electrons are
confined to a number of bands of energy, and forbidden from other regions. The
term "band gap" refers to the energy difference between the top of the valence
band and the bottom of the conduction band. Electrons are able to jump from one
band to another. However, in order for an electron to jump from a valence band
to a conduction band, it requires a specific minimum amount of energy for the
transition. The required energy differs with different materials. Electrons can
gain enough energy to jump to the conduction band by absorbing either a phonon
(heat) or a photon (light). A semiconductor is a material with a small but
nonzero band gap which behaves as an insulator at absolute zero but allows
thermal excitation of electrons into its conduction band at temperatures which
are below its melting point. In contrast, a material with a large band gap is an
insulator. In conductors, the valence and conduction bands may overlap, so they
may not have a band gap.The conductivity of intrinsic semiconductors is strongly
dependent on the band gap. The only available carriers for conduction are the
electrons which have enough thermal energy to be excited across the band gap.

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