When All You Have Is a Covalent Model of Bonding, Every Substance Is a Molecule: A Longitudinal Study of Student Enactment of Covalent and Ionic Bonding Models

This longitudinal study examines the responses of students at two different institutions to creative exercises related to models of chemical bonding. Questions in the form of creative exercises required students to provide relevant, accurate, and distinct statements about two compounds for which they were provided only the formula and electronegativity values: SCl2 and CaCl2. Students responded to the questions at the end of general chemistry, six months later, and one year later. Their responses were analyzed qualitatively and quantitatively to explore patterns in application of bonding ideas and change over time. The data reveal extensive application of covalent bonding ideas to an ionic compound, regardless of whether a student identified the substance as ionic or not, and that this is consistent over a year out. Implications for instruction of bonding models in general chemistry (and beyond) are discussed.