Valenzbänder

Valenzbänder, also known as valence bands, are a fundamental concept in solid-state physics and chemistry, crucial for understanding the electrical properties of materials. In crystalline solids, electrons occupy distinct energy levels. When atoms form a crystal lattice, these discrete energy levels broaden into bands due to the interactions between neighboring atoms. The valence band is the highest energy band that is completely filled or partially filled with electrons at absolute zero temperature. These electrons in the valence band are responsible for chemical bonding within the material.

The behavior of electrons in the valence band dictates whether a material is a conductor, semiconductor, or insulator. In conductors, the valence band either overlaps with the next higher energy band (the conduction band) or is only partially filled, allowing electrons to move freely with minimal energy input, thus conducting electricity. In semiconductors, there is a small energy gap, known as the band gap, between the valence band and the conduction band. Electrons can gain enough energy from thermal excitation or other sources to jump across this gap and contribute to conductivity. Insulators have a large band gap, meaning a significant amount of energy is required to excite electrons from the valence band to the conduction band, making them poor conductors of electricity. The properties of the valence band, including its width and the energy of its electrons, are determined by the atomic structure and the types of elements forming the material.