Symmetry rules in chemisorption

A MO theory of chemisorption is presented that relates the structure of the adsorption site to the group orbital local d. of states at the Fermi level projected out from the surface MOs by the adsorbate orbitals. Preferential adsorption of CO to \"on-top\" sites of the faces of noble metals such as Ni, Pt, and Rh is ascribed to the subtle balance between on-top directing interactions with the metal valence d-electrons and bridge coordination directing interactions with the metal valence s-electrons. The difference in hydrogenolysis behavior between Ni and Pt is explained