CHM 501

37. Magnesium has the filled s2 electron configuration yet is still a metal. Give an explanation for this in terms of a metallic bonding description.

Answer

The electron configuration for Mg is [Ne]3s2 and Z* is about 2.85 (using Slater's rules). As the bands begin to form, the energies of both the s and p orbitals begin to spread out and since Z* is of moderate value, the p orbital energies are close to the s orbital energies. This means that upon band formation the top of the s-band is above the bottom of the p-band, i.e., the bands overlap in energy. This allows electrons from the s-band to occupy the p-band, leaving both bands partially occupied, which leads to the metallic character.