Understanding ionic bonding – a scan across the Croatian education system

Abstract

A study was conducted on the understandings of the accepted model of ionic substances that are held by participants at all levels of the chemical education system in Croatia, including secondary school students, university students, and chemistry teachers. We follow the research of Taber who found that a diagram of a layer of a sodium chloride crystal can be perceived by students as due to electrostatic attractions, consistent with the currently accepted view, or in an alternative molecular framework in which ionic bonding is seen as the process of electron transfer from one atom to another. A Croatian translation of the instrument used by Taber was administered to 650 secondary school students, 264 tertiary undergraduate students, and 86 teachers of chemistry at the secondary level. It was found that significant percentages of the participants, including teachers, interpreted the diagram with conceptions consistent with the molecular framework. Significant numbers of participants at all levels showed evidence of beliefs consistent with Taber's categories of a history conjecture (ionic bonds exist only between the partners in electron transfer), a valency conjecture (the number of ionic bonds that an ion can form is dependent on the electron configuration of the parent atom and is related to the number of electrons gained or removed to form a “stable octet”), and a “just forces” conjecture (ionic bonds involve something more than forces of attraction). The existence of alternative conceptions of ionic bonding at all levels of the education system, including among the teachers, is a situation of considerable concern. Obviously the pedagogical content knowledge of teachers cannot be based on an inadequate level of content knowledge. Remedial action seems to be important. As a first step, we speculate on the possible sources of the alternative conceptions. This includes an analysis of the chemical validity of the subject matter that is commonly presented in textbooks.