We present an approach to the question of the educational relations between chemistry and physics based on the one hand, on an inferentialist account of scientific representation (Suárez M., (2024), "Inference and Representation. A Study in Modelling Science," Chicago and London: The University of Chicago Press). On the other, we have drawn on the notion of science identities, as is currently used in science education. We argue that the representational practices of chemistry are the key competencies for the development of a chemistry identity. We extrapolate this conclusion to physics. The problem of representational plurality, that is, that some objects can be represented divergently in these sciences is thus linked to that of identity plurality, to the question of whether it is possible for a person to simultaneously hold a chemistry and a physics identity. We study the educational implications of this situation within the framework of Lev Vygotsky's sociocultural pedagogy to conclude that the difficulties inherent to representational plurality in chemistry and physics are sociological: university degrees are built around a single, well-defined, identity, thus tending to exclude any form of plurality that compromises this uniformity. As an application of these conclusions, we have studied the question of the introduction of the quantum description of molecules in chemistry education at an undergraduate level. We conclude that this introduction should not be based on the molecular orbitals approach but, instead, on the valence bond method.