The origin of the conduction band in table salt

A long-standing misinterpretation of the origin of the conduction band in sodium chloride is corrected. We show that this band is primarily derived from chlorine states, and not from sodium states as is generally believed. The anion character of the conduction band holds for the other alkali halides as well. The reinterpretation of this band clarifies why the size of the band gap in these insulators does not depend on the alkali metal in a first-order approximation