We examined the combined effect of atomic under- and hetero-coordination on the bond relaxation and electronic binding energy of Sc, Zr, and ScZr alloying using a combination of the bond-order-length-st rength (BOLS) correlation and density functional theory (DFT) calculations. Observations strongly emphasize the relevance of core-level shifts as reliable X-ray photoelectron spectroscopy experimental descriptors of core-shell catalysis reactivity, along with under-coordinated atoms in bimetallic transition metal systems. The BOLS-DFT method provides enhanced catalysis reactivity and detects surface and alloy configurations, opening up the possibility to investigate more complex systems with irregularly under- and hetero-coordinated atoms. (C) 2016 Elsevier B. V. All rights reserved.