Based upon our previously developed microscopic model of intergranular embrittlement in A3B L12intermetallic compounds, it is shown that a plot of A versus B s-orbital electronegativity leads to a clear discrimination between ductile and brittle materials. A structure-property relationship is uncovered by constructing the associated structure map using phenomenological Mendeleev numbers, which exhibits a topology identical to the ductile-brittle property map.