The empirical bond energy bond order (BEBO) approach has been extended in order to make predications of the energies of activation of reactions for H2 and O2 on transition d-metals. Thus

for the Rideal-Eley mechanism of the surface reaction the 24 d-metals with different catalytic properties are predicated to be approximately classified into four groups A

B

C and D. In accordance with Langmuir-Hinshelwood mechanism

the surface reaction for each of the 24 d-metals has higher energy of activation or reaction potential energy than these from the Rideal-Eley mechanism reasoning. In this paper

favourable comparisons are made between the results of this approach and available experimental data. The "low chemisorption heats -high catalytic activities" rule for some catalytic oxidation reactions has been fully discussed.