Electronegativity and Its Multiple Faces: Persistence and Measurement.

JUAN CAMILO MARTÍNEZ GONZÁLEZ; KLAUS RUTHENBERG

Florida

Congreso; International Society for the Philosophy of Chemistry Summer Symposium; 2016

Florida Atlantic University

Electronegativity is one of the most relevant concepts in chemistry used to explain many aspects of reactivity. This concept has a long existence in the knowledge of chemists but it was only defined qualitatively with the advent of the theories of bonding as ?the power of an atom in a molecule to attract electrons to itself? (Pauling 1932). However, the concept itself is far from being precisely determined, and this problem is mainly due to the fact that electronegativity cannot be measured by direct means, and must be inferred on the basis of other properties that can be directly measured. There are two main methods of computing electronegativity: (i) a spectroscopic method, based on the ionization potential I of the isolated atom, and (ii) a thermodynamic method, which uses the enthalpy ΔH° of formation of the molecule. Although usually presented as two ways of measuring a single property, these two methods lead to different concepts. According to the spectroscopic method, electronegativity is an intrinsic property of the atoms. The thermodynamic method considers the atoms in the context of the molecules and, as a consequence, electronegativity is conceived as a relational property. Although this concept is very successful and widely used, neither a more than intuitive definition nor a generally accepted and standardized quantification modelhave been developed. Electronegativity is presented and discussed with respect to its main conceptual and operational continuities and discontinuities. In this paper, we try to analyze the epistemological status of electronegativity, taking the latter as a typical example from the chemical sciences. By ?epistemological status? we subsume the following issues: the question of the reference of electronegativity, its historical persistence, and the relation between (empirical) measurement and (theoretical) quantification.