Complex sentence: His six "affinities acting within a cycle" anticipate both the electron, modern theories of aromaticity and arguably since he recognised that affinities have direction and are not merely point particles, even the wave mechanical theories of the 1920s.
Split into simpler sentences: His six "affinities acting within a cycle" predated both the discovery of the electron and modern theories of aromaticity. Armstrong recognised that affinities have direction and are not merely point particles, and so he might be said to have anticipated parts of the wave mechanical theories of the 1920s.