Electronic partition function ($q_{\mathrm{el}}={\sum }_i{g}_i{e}^{-{\epsilon }_i/kT}$)

The electronic partition function includes electronic excitation energies and degeneracies $g_i$. If only an exactly degenerate ground manifold of size $g$ is populated, $q_{\mathrm{el}}=g$ and its molar entropy is $R\log g$. Resolved splittings require a state sum rather than replacing all components by one degeneracy.