In the group exercise described, students are guided through an inductive justification for the spin conservation selection rule ([delta]S = 0). Although the exercise only explicitly involves various states of helium, the conclusion is one of the most widely applicable selection rules for the interaction of light with matter, applying, in various ways, to atoms and molecules of all sizes. Connections are made among several concepts routinely covered in physical chemistry courses including the Pauli Principle, orthonormal wave functions, overlap integrals, atomic term symbols, multiplicity, radiative lifetimes, fluorescence, and phosphorescence. Detailed student directions are included in the Supporting Information.