Edward Frankland realizes that there are specific valences for atoms. Archibald Scott Couper and August Kekulé simultaneously realize that specific atoms bond to specific other atoms in molecules, particularly carbon with valence 4, and invent ways of drawing this on paper. Kekulé also solved the problem of bonding within the compound benzene, after (so he later told it) a dream. My supporters at Patreon get a reference sheet to view for images of molecules.Support the show