Using Atomic Orbitals and Kinesthetic Learning To Authentically Derive Molecular Stretching Vibrations

Abstract

The stretching modes of MLx complexes have the same symmetry as the atomic orbitals on M that are used to form its σ bonds. In the exercise suggested here, the atomic orbitals are used to derive the form of the stretching modes without the need for formal group theory. The analogy allows students to help understand many conceptually difficult aspects of the vibrational spectroscopy of polyatomic molecules, including IR activity, degeneracy, and orthogonality. The approach intentionally requires active participation and is nonmathematical and “low tech”. It is suitable for large classes of chemistry majors and nonmajors.