Metals, band theory diagram

Molecular orbital (MO) theory has been used to explain the bonding in metallic crystals, such as pure sodium or pure aluminum. Each MO, instead of dealing with a few atoms in a typical molecule, must cover the entire crystal (might be 1020 or more atoms ). Following the rule that the number of MOs must equal the number of atomic orbitals (AOs) combined, this many MOs must be so close on an energy level diagram that they form a continuous band of energies. Because of this factor, the theory is known as band theory. 

Phase Diagrams (P versus T) 13-14 Amorphous Solids and Crystalline Solids 13-15 Structures of Crystals 13-16 Bonding in Solids 13-17 Band Theory of Metals... 

The fundamental concept of band theory is to consider the energies of the molecular orbitals in an assembly of metal atoms. An MO diagram describing the bonding in a metallic solid is characterized by having groups of MOs (i.e. bands)... 

The main features of the optical absorption and emission spectra of transition metal complexes can be interpreted on the basis of crystal-field or ligand-field theory. Generally, the energies of the absorption and the emission bands correspond to energetic differences between electronic states. Therefore, an interpretation of the optical spectra will start with a comparison between the experimental spectra and the term diagram of the complex ion, according to the crystal-field theory. This procedure will be demonstrated by two informative examples. 

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