This paper aims to investigate the presentation of the concept of valence in college-level, general chemistry textbooks published in the USA between the 1890s and the 1940s. The delimited period covers the emergence of theories about atomic structure, electronic distribution and chemical bonding. Transition from the classical concept of valence (as the combining power of a chemical element), which resulted from either the analysis of formulas of compounds or experimental results, into the concept related to the electronic structure of elements, according to which the valence is determined by the number of electrons in the last shell, was observed. In general, valence was presented in textbooks in order to serve as an instrument for the writing of formulas of compounds, and historical approaches to the construction of the concept were not contemplated by the authors.

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.

RESUMO Este artigo propõe uma análise de aspectos epistemológicos e didáticos dos programas e de algumas questões de química do vestibular Fuvest, referentes ao período de 1980 a 2018. A análise se volta para os critérios que orientaram a seleção e organização dos conteúdos; as relações sugeridas entre os níveis macroscópico e submicroscópico da matéria; o uso de modelos de partículas para explicação dessas relações; a experimentação e a contextualização do conhecimento químico. Observou-se uma grande mudança do programa em 1991 e outra, de menor extensão, em 2002, as quais podem ser relacionadas a mudanças em diretrizes curriculares estaduais e federais. O processo aqui delineado, de incorporação ao vestibular de tendências originadas na pesquisa em ensino de ciências, pode ensejar reflexões úteis aos educadores em química.

ABSTRACT This paper proposes an analysis of epistemological and didactic aspects of Chemistry programs and of some Chemistry questions of the University of São Paulo admission exam (Fuvest) from 1980 to 2018. Our analysis focuses on the criteria guiding the selection and organization of contents; on the implied relationships between the macroscopic and submicroscopic ontological levels of matter; on the use of particle models to explain such relationships; on experimentation and on the contextualization of chemical knowledge. There was a major change in the program in 1991 and a minor one in 2002, which may be related to changes in state and federal curriculum guidelines. The process outlined here, in which Science education research results influenced university admission exams, may lead to useful reflections for educators in chemistry.

Resumo: Neste artigo foi analisado o emprego de diagramas de energia de orbitais em livros didáticos de Química Geral, utilizados no ensino universitário brasileiro ao longo do século XX. Para isso, 16 livros publicados entre 1950 e 2001 foram selecionados, e a semiótica peirceana foi utilizada como referencial de análise para o entendimento sobre diagramas. A análise revelou que o uso de diagramas de energia de orbitais ocorre em diferentes contextos de aplicação e com diferentes objetivos. Do ponto de vista da semiótica, os significados dos signos que compõem os diagramas, e as regras que orientam sua construção e operação, são previamente convencionados, fornecendo, assim, bases mínimas a respeito de como interpretá-los. Todavia, aspectos mais sutis se afastam dessa base mínima e podem acarretar interpretações não pretendidas por seus autores. Tais concepções alternativas podem ser superadas através de compreensões mais elaboradas sobre a natureza e o papel das representações no ensino, fundamentadas na semiótica Peirceana.

Abstract: In this paper the use of orbital energy diagrams in General Chemistry textbooks used in Brazilian universities throughout the twentieth century was analyzed. Sixteen textbooks published between 1950 and 2001 were selected. C. S. Peirce’s semiotics was chosen to analyze the use of energy diagrams in the textbooks. The analysis revealed that the use of orbital energy diagrams occurs in different contexts and with different goals. From a semiotic point of view, the meanings of the signs that make up the diagrams and the rules guiding their construction and operation are previously agreed, thus providing the foundations for their interpretation. However, more subtle aspects deviate from such foundations and may result in interpretations that were unintended by the textbooks authors. Such misconceptions may be overcome by means of more elaborate insights into the nature and the role of representations in teaching, such as those arising from Peircean semiotics.

This paper presents an overview of the development of chemical education as a research area and some of its contributions to society. Although science education is a relatively recent area of research, it went through an expressive development in the last decades. As in the whole world, in Brazil also such development is attested by the expressive number of scientific societies, specialized journals, and meetings with growing attendance in the areas of science education in general and chemical education in particular. Following are the main contributions of research in science education related to chemistry teaching: adoption of teaching-learning principles in chemistry education; contextualization of chemical knowledge; interdisciplinary approach to chemistry teaching; use of the history of science for the definition of contents and for the design of curricula and teaching tools; development of specific disciplines for the initial and in-service training of chemistry teachers; publication of innovative chemistry textbooks by university-based research groups; elaboration of official guidelines for high-school level; and evaluation of chemistry textbooks to be distributed to high-school students by the Brazilian government. In spite of a positive impact of such initiatives, science education in Brazil still faces many problems, as indicated by poor results in international evaluations (such as the Program for International Student Assessment). However, changes in such a scenario depend less on the research in chemical education than on the much-needed governmental initiatives aiming at the improvement of both attractiveness of teaching career and structural conditions of public schools. In conclusion, new government investments in education are necessary for continuing the development of chemistry; moreover, scientific societies and decision makers in educational policies should take into consideration the contributions originated from the chemical education research area.

Este trabalho analisa os seis livros didáticos de química indicados pelo Programa Nacional do Livro Didático para o Ensino Médio em 2007 (PNLEM 2007), no que se refere a seus conteúdos de história da ciência. Para isso, partiu-se do instrumento de análise desenvolvido por L. Leite (2002), que foi adaptado para a presente investigação. Os resultados obtidos indicam, como tendência geral, que a história da ciência é apresentada nos livros didáticos de maneira linear e superficial, constando, sobretudo, de nomes e datas. Dessa maneira, concluímos que os conteúdos de história da ciência desses livros não contribuem para que os alunos desenvolvam uma imagem do empreendimento científico condizente com os objetivos educacionais da atualidade.

This paper aims to analyze the history of science content of six chemistry textbooks selected in 2007 by the Brazilian National High School Textbook Program (PNLEM 2007). An analysis instrument originally developed by L. Leite (2002), and modified for the present investigation, was used. Results indicate that, in general, the history of science is presented in chemistry textbooks in a linear and superficial fashion, consisting mostly of the mere mention of names, facts and dates. One can conclude that the history of science content of the analyzed textbooks do not contribute to help students to develop an image of the scientific endeavor in keeping with current educational goals.

This paper aims at analyzing the history of science content of three general chemistry textbooks used in Brazilian universities: the translations of Kotz and Treichel's Chemistry & Chemical Reactivity, Atkins and Jones's Chemical Principles, and Garritz and Chamizo's Química. Results revealed different trends for the inclusion of history of science in chemistry teaching. Kotz & Treichel and Atkins & Jones used history mainly as curiosity and ornament. Garritz & Chamizo adopted the historical approach as one of the organizing axis of their textbook. Nevertheless, the historical content of the three textbooks may be criticized from current historiographical standpoint.

Os livros didáticos, ao promoverem a circulação de ideias, valores e comportamentos desejados em determinados períodos, constituem importante ferramenta no levantamento da história de uma disciplina. Propõe-se investigar, nesse contexto, qual foi e qual é o papel dos livros didáticos na formação profissional em química, e que lugar eles vêm ocupando na dinâmica das salas de aula, tomando como locus de pesquisa uma importante universidade pública brasileira. Considerando-se fundamentos da história oral, foram entrevistados seis professores, cuja formação e atuação docente ocorreram em diferentes períodos da história da instituição. Os depoimentos sobre o papel do livro didático em suas vidas acadêmicas, como alunos e docentes, permitiram observar diferentes tendências desde o período em que o ensino de química permaneceu centrado na figura do professor até a recente opção pela adoção de um único livro didático como guia para o desenvolvimento de uma disciplina.

Textbooks constitute important research tools for the history of education, since they promote the circulation of the desired ideas, judgments and behaviours in a specific period. In this context, this paper focuses on the textbook's role in general chemistry courses in different periods, assuming as a research locus a major Brazilian public University. Considering the fundamentals of oral history, six lecturers, whose training and professional work developed in different periods of the history of the institution, were interviewed. The reports about the role of the textbook in their academic lives as students and lecturers revealed different tendencies from the lecturer-centered process of the early years, to the suggestion of using several textbooks, to the recent adoption of a single textbook as a guide to the general chemistry course.

This paper focuses on the early interpretations of the concept of gas, originally created by J. B. Van Helmont (1579 <FONT FACE=Symbol>¾</FONT> 1644). Our main interest is on the ideas of English physicians and chemical philosophers of the seventeenth century. Gas was usually associated with the material cause of diseases, with the vital spirit, or with a volatile spirit produced in some kinds of material transformations. As a general trend, however, the authors who did not want to embrace the details of the medico-chemical system proposed by Van Helmont preferred to use more well-known words (such as vapours, exhalations, effluvia, odours, spirits), avoiding the use of the neologism.

The word gas was coined by the "chemical philosopher" Joan Baptista Van Helmont (1579 -- 1644) to name a very broad concept in his chemico-medical system. Eventually, some physicians who followed Helmontian ideas adopted the concept. The present paper aims to analyze the reception of the original idea of gas by an English Helmontian physician, George Thomson (1619 -- 1677). Thomson wrote that the "material cause" of the plague was a gas, and compared it to the "Gas of sulphur". He also related the human archeus to a gas, and explained some observations in the laboratory in terms of production of gases. We observe, however, that Thomson was not as interested as Van Helmont in discussing details about the structure of the matter. Thus, gas did not have the same relevance in Thomson's work as it had in Van Helmont's.

Several authors in the 17th century used the atomic hypothesis to explain observable phenomena. This paper analyzes some ideas about chemical transformation proposed by the English physician Walter Charleton. In Physiologia Epicuro-Gassendo-Charltoniana (London, 1654), Charleton examined philosophical aspects of the atomic theory, and suggested that the best explanation for all natural phenomena would be only in terms of atoms and their motions. Sometimes, however, he had to attribute to the atoms some kind of "internal virtue", to explain more complex properties of the matter. His idea of "element", and the little use of experimentation and quantification, also limited the range of Charleton's theory.