A type of correlation diagram in which the molecular energy levels are drawn as a function of bond angles rather than as a function of intermolecular distance. These diagrams were first constructed by Arthur Donald Walsh (1916–77) in 1953, building on earlier work by Robert Mulliken. The conclusions he drew are known as Walsh’s rules. Walsh diagrams have been used extensively to predict molecular shapes. As with VSEPR theory, the valence electrons determine the molecular shape.