How Do Inorganic Students Represent Molecular Orbitals? A Multi-Institutional Study from the Foundation-Level Inorganic Chemistry Course

This investigation of student and instructor representations of molecular orbitals (MOs) uses the knowledge from a community of practice to build collective pedagogical content knowledge of student understanding of molecular orbital representations in the foundation-level inorganic chemistry course. Participants were asked to sketch the bonding and antibonding MOs of a lithium hydride molecule. The student-generated images of MOs were analyzed and characterized according to five criteria: the atomic orbitals chosen, the sign of the wavefunction, the relative contribution of the atomic orbitals to the molecular orbitals, the overlap of atomic orbitals, and the shape of the MOs. While most students correctly chose a basis set and accurately represented the sign of the wavefunction for the MOs, they were less successful at sketching the relative contribution of the atomic orbitals to the molecular orbitals, the overlap of atomic orbitals, and the shape of the MOs. Students have an incomplete understanding of the information encoded in MO sketches and may not attribute meaning to these pictures in the same way that instructors may. These results suggest that instructors need to help students develop representational competence in order to achieve a more expert-like understanding of MO representations and to connect these depictions to the properties of molecules.