We also assume that the overlap matrix element is proportional to the coupling element, S = -αV ak , where α is another constant which is identical for all metals. The only free parameters in the model for a given adsorbate are α and β, which are independent of the metallic surface species. We obtain these parameters by fitting E chem to the DFT energies in Figure . Table shows the least-squares errors fitted α and β for C* and O*. Note that E chem is multiplied by 3 to account for three bonds due to the preferred adsorption site being the hollow site (see SI Section V for ontop site fitting). Figure ) shows parity plots for fitted chemisorption energies from the model vs. computed DFT energies.