energy bands

Energy bands are ranges of energy levels that electrons can occupy in a solid material. In materials like metals, electrons can move freely within certain energy bands, allowing electrical conductivity. In insulators and semiconductors, these bands are separated by energy gaps: the valence band (full of electrons) and the conduction band (where electrons can move freely). Electrons need enough energy to jump across this gap to conduct electricity. These bands arise from the collective behavior of many atoms' electrons, shaping the material's electrical, optical, and thermal properties.