Conceptualisation of Lewis structures by chemistry majors

Lewis structures are the simplest model for students to communicate chemical information using chemical symbolic language. Thus, competence in Lewis structures is essential to progress in the study of chemistry. Proposals on how to teach/learn Lewis structures with inert rules abound, nonetheless, scant related educational research has been conducted. The present study is part of a larger investigation into the conceptualisation and use of Lewis structures by novices and experts. This study analysed data from a cross-sectional, 122-participant sample of chemistry majors at a large university in Costa Rica. Participants were prompted to draw Lewis structures, which rendered information on their representational competence. Analysis of mistakes in their representations shed light on participants’ conceptualisation of Lewis structures. Responses to open-ended items further contributed in elucidating their conceptualisation. Findings suggest: (a) participants’ competence to draw Lewis structures is deficient throughout the major; (b) participants relied significantly on memory and familiarity and not on understanding to draw Lewis structures; (c) most participants’ limited understanding of Lewis structures stems from their using mental images and propositional representations for Lewis structures instead of mental models. Use of appropriate mental models could enable individuals to explain and predict chemical behaviour based on Lewis structures.