Theories: Band Theory of Solids

Band theory of solids explains how atoms in a solid interact to create different electrical behaviors. When atoms come together, their electrons form overlapping energy levels, creating continuous ranges called energy bands. If electrons can move freely within these bands, the material conducts electricity (conductors). If they are restricted and there’s a gap between filled and empty bands, the material acts as an insulator or semiconductor. Essentially, band theory helps us understand why some materials conduct electricity well, some don't, and how their electronic properties change under different conditions.