> This situation is different in metals. The atoms form a dense, homogeneous lattice with sparsely-populated orbitals that essentially merge together, extending throughout the material and no longer exhibiting clearly-quantized energy levels that are characteristic of electrons bound to a single nucleus.
With quantum mechanics, we can sort of solve three-body problem of the H_2^+ molecule, that is two protons and an electron. With larger amount of atoms one has to make use of approximation methods, like the perturbation theory.
For two atoms, quantum physics predicts that the valence electrons which had the same energy when atoms were separated, split into two different but close energy states when atoms are close together. One can think of those states as the state where electrons "orbits" in such way that it is present between atoms, one one state where electrons "orbits" around two atoms at once.
With the very large amount of atoms in a macroscopic solid, this results in the number of energy levels that is proportional to the number of atoms, but where gaps between those quantized levels are very small. This means that it is easier to treat this dense set of very close energy levels not as quantized energy levels, but as an energy band (hence: electronic band structure).
> This situation is different in metals. The atoms form a dense, homogeneous lattice with sparsely-populated orbitals that essentially merge together, extending throughout the material and no longer exhibiting clearly-quantized energy levels that are characteristic of electrons bound to a single nucleus.
With quantum mechanics, we can sort of solve three-body problem of the H_2^+ molecule, that is two protons and an electron. With larger amount of atoms one has to make use of approximation methods, like the perturbation theory.
For two atoms, quantum physics predicts that the valence electrons which had the same energy when atoms were separated, split into two different but close energy states when atoms are close together. One can think of those states as the state where electrons "orbits" in such way that it is present between atoms, one one state where electrons "orbits" around two atoms at once.
With the very large amount of atoms in a macroscopic solid, this results in the number of energy levels that is proportional to the number of atoms, but where gaps between those quantized levels are very small. This means that it is easier to treat this dense set of very close energy levels not as quantized energy levels, but as an energy band (hence: electronic band structure).