This paper presents the contributions of Alcindo Flores Cabral (1907-1982), professor of chemistry at the Faculdade de Agronomia Eliseu Maciel, nowadays part of the Universidade Federal de Pelotas, to chemistry teaching, a contribution almost unknown to the Brazilian chemical community, although recognized as valuable by several renowned chemists abroad, such as W. Hückel, G. Charlot, F. Strong, E. Fessenden and others. Cabral's innovative helicoidal representation is presented not only in connection not only with contemporary representations, but it also includes an incursion into the first helicoidal systems proposed, those of Hinrichs and of Baumhauer. Some comments are made on Cabral's Classificação natural dos elementos, published in 1946, and also on other texts that he wrote to make chemistry teaching more effective.
Periodic table; Natural classification of elements; History of chemistry in Brazil; Cabral
