Challenges to the Structural Conception of Chemical Bonding

While the covalent bond plays a central role in chemical predictions, interventions, and explanations, it is a difficult concept to define precisely. This paper investigates the structural conception of the covalent bond, which says that bonding is a directional, sub-molecular region of electron density located between individual atomic centers that is responsible for holding the atoms together. Several approaches to constructing molecular models are considered in order to determine which features of the structural conception of bonding, if any, are robust across these models. The paper concludes that key components of the structural conception are absent in all but the simplest quantum mechanical models of molecular structure, seriously challenging the conception’s viability. Crucial to chemical practice and discourse is the notion of the chemical bond, specifically the covalent bond. For most synthetic and analytical purposes, molecules are conceived of not just as collections of atoms, but ∗Earlier versions of this paper were presented at the Australia National University, the Philosophy of Science Association, and the Center for Philosophy of Science, University of Pittsburgh. I am grateful to these audiences for their enthusiasm and very helpful comments. Special thanks to Jerry Berson, Barry Carpenter, Dave Chalmers, Peter Godfrey-Smith, Clark Glymour, Robin Hendry, Roald Hoffmann, Paul Needham, John Norton, Janet Stemwedel, and Deena Skolnick Weisberg for extremely helpful feedback.