The concept of Valence Band and Conduction Band forms the foundation of the Energy Band Theory in Class 12 Physics (Semiconductor Electronics chapter).
Valence Band: Full of bound electrons; cannot carry current.
Conduction Band: Free electrons; carries current.
Energy Gap: Determines whether material is conductor, semiconductor, or insulator.
The key difference between materials is the Energy Gap (Eg) between the two bands:
| Material | Energy Gap |
|---|---|
| Conductor (copper) | No gap (bands overlap) |
| Semiconductor (silicon) | Small gap (~1 eV) |
| Insulator (rubber) | Large gap (~5 eV or more) |
The valence band contains tightly bound outermost electrons of atoms. The conduction band is the higher energy band where electrons are free to move and conduct electricity. The energy gap between them determines if a material is a conductor, semiconductor, or insulator.
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