Having fit α and β to chemisorption energies from DFT, we compute the variation of E chem for O* and C* with ϵ d for 3d, 4d and 5d series of transition metals shown in Figure ) respectively. Note that for a fixed row, the chemisorption energy is a function of only ϵ d , as V 2 ak and w d for each row of the periodic table are functions of ϵ d .