  It has been shown recently that chemical bond lengths, in general, like those
in the components of nucleic acids, caffeine related compounds, all essential
amino acids, methane, benzene, graphene and fullerene are sums of the radii of
adjacent atoms constituting the bond. Earlier, the crystal ionic distances in
all alkali halides and lengths of many partially ionic bonds were also
accounted for by the additivity of ionic as well as covalent radii. Here, the
atomic structures of riboflavin and its reduced form are presented based on the
additivity of the same set of atomic radii as for other biological molecules.
