Ontological and epistemological status of the concept of orbital in twentieth-century General Chemistry textbooks

Author(s)

Evandro Fortes Rozentalski

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2013-12-06

Examining board members

Paulo Alves Porto; Waldmir Nascimento de Araujo Neto; Osvaldo Frota Pessoa Junior

• Advisor: Paulo Alves Porto

Abstract

One of the topics discussed in the Philosophy of Chemistry is the scientific realism of chemical concepts, such as the concept of orbital. The ontological status (reference to reality or not) of orbitals became the subject of intense debate as from 1999, when a paper by Zuo and colleagues was published and supported without major precautions by an editorial of the journal Nature, which stated that orbitals had been observed directly. In such debate, both ontological and epistemological aspects were raised, about what orbitals are, and the possibility of observing them. These points have implications for Chemistry and especially for Chemical Education. This research aims to investigate how the concept of orbital was presented in undergraduate General Chemistry textbooks throughout the twentieth century. Textbooks used in Brazil during that period were selected by simultaneous identification in the following databases: the catalogs of the libraries of the University of São Paulo (USP), Federal University of Rio de Janeiro (UFRJ), and the site Estante Virtual which gathers the collections of several Brazilian bookstores. Twenty-six General Chemistry textbooks were selected and investigated, covering the period from 1911 to 2001. Analysis of the textbooks, based on the selected theoretical framework, resulted in the following categories: conceptual basis of the orbital; iconic representation of the orbital, and symbolic representation of the orbital. The first is mainly, but not only, based in the debates about the ontological and epistemological status of the orbital in the literature. The last two are based on Peircean semiotics. The concept of orbital began to be introduced and discussed in General Chemistry textbooks in the second half of the twentieth century. In the first category, it is noted that most of the textbooks define the orbital as a region in which it is more likely to find the electron, in terms of probability density. For some philosophers of chemistry such understanding is an indication of a peculiar appropriation of Wave Mechanics by chemists. In the second category, the images of orbitals whose characteristic semiotics consists in the representation of qualities such as their shape are mostly identified as areas of high probability density, and represented by continuous and uniform surfaces. These images convey a secondary role to the electron. Finally, in the third category, whose characteristic semiotics consists in conventionalizing the sign meaning beforehand to the reader, it is verified that orbital diagrams, in which orbitals are represented by horizontal lines and electrons by arrows, suggest that orbitals and electrons are two distinct entities. Such conception implies the understanding that filled and empty orbitals have ontological equality. In conclusion, the analysis show that the concept of orbital is introduced by twentieth-century General Chemistry textbooks in a non-problematized manner, if one considers both the conceptual standpoint and the meanings of the different representations of the concept. (AU)

• FAPESP's process: 11/15295-0 - The concept of orbital in university-level general chemistry textbooks in the twentieth century
• Grantee: Evandro Fortes Rozentalski
• Support Opportunities: Scholarships in Brazil - Master