An Exploration-Based Activity to Facilitate Students’ Construction of Molecular Symmetry Concepts

Molecular symmetry is a topic that requires mental manipulation of molecules when searching for symmetry elements and their corresponding symmetry operations. Such mental activities are difficult for students in a traditional classroom where only definitions and demonstrations are provided. Therefore, an exploration-based activity was developed to help university chemistry students construct molecular symmetry concepts. Since symmetry is a mathematical concept, Pirie and Kieren’s model of growth of mathematical understanding was used as the framework to design the activity. Each task allowed students to self-construct the meaning of symmetry by performing an operation on 2D figures and/or 3D manipulatives. The activity was designed for students without a background in molecular symmetry and conducted at two public universities. In class, the students went through stages of understanding that were consistent with those in the model. The results from the conceptual test confirmed that they were able to apply the learned concepts to identify the symmetry elements and symmetry operations of the given molecules.