Chemistry in the xixth century has built a «chemical atom» that has permitted to write formulae and chemical equations, to relate properties of substances with their structure, to assign a valence to the elements and to classify chemical elements in a periodic table. But many chemists didn't agree with the real existence of the particle «atom». It was necessary to obtain new evidences until a general acceptance the «physical atom» was achieved: a complex particle with an internal structure. In this paper some ideas derived from the analysis of textbooks in the first half of the xxth century are proposed. The final conclusions (transitory, because the research is not ended) show the evolution of the rhetoric and the explanations about the structure of the electronic atom and, also, the influence of the periodic table in its. Several considerations about teaching chemistry will be mad
