BETWEEN TYPES AND RADICALS: THE CONSTRUCTION OF THE CONCEPT OF VALENCE

This paper presents a historical case study regarding the development of the concept of valence in late nineteenth and early twentieth centuries. The case study focuses on Edward Frankland’s contribution to the process which lead to the convergence of two theories about the combination of the elements: the theory of types and the theory of radicals. Results show how such process involved many other scientists from various countries and how the concept of valence related to studies on bonding, periodicity and chemical structure. Changes in the nomenclature and notation were also observed. In the beginning of the twentieth century, the empirical concept of valence received theoretical explanations under the light of the then new theories on electronic structure of atoms. Thus, this case study exemplifies the complexity of the process of development of a scientific concept and, in particular, shows the multiplicity of connections of the concept of valence in the body of chemical knowledge.