O CONCEITO DE VALÊNCIA EM LIVROS DIDÁTICOS DE QUÍMICA GERAL ENTRE AS DÉCADAS DE 1890 E 1940

• Autor(a) principal: Nogueira,Helena S. Alvares
• Data de Publicação: 2019
• Outros Autores: Porto,Paulo Alves
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Química Nova (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-40422019000200237
• topic: general chemistry; textbooks; valence; higher education; chemistry teaching; history of chemistry

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.