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Question
Sn, C, and Si, Ge are all group XIV elements. Yet, Sn is a conductor, C is an insulator while Si and Ge are semiconductors. Why?
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Solution
The conduction level of any element depends on the energy gap between its conduction band and valence band.
In conductors, there is no energy gap between the conduction band and valence band. For insulators, the energy gap is large and for semiconductors the energy gap is moderate.
The energy gap for Sn is 0 eV, for C is 5.4 eV, for Si is 1.1 eV and for Ge is 0.7 eV related to their atomic size.
Therefore Sn is a conductor, C is an insulator, and Ge and Si are semiconductors.
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