New formulation is introduced to model surface oxidation of soot particles. In the new development, the surface is represented by an arbitrary number of reactive sites and their physically-founded transformations. The latter are combined and integrated with gas-phase and particle-dynamics models. The surface reaction model defines two state properties and establishes a structural relationship between them that guides evolution of the surface. This new model form for the surface-chemistry led to close reproduction of shock-initiated oxidation of soot: CO profiles in two experiments performed at substantially different temperatures, 1990 and 2780 K, as well as CO production rates over a wide range of temperatures, 1652-3130K, all without employing the parameter-a empiricism of the previous model formulation. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.