The 2p(3/2) core-level binding energy (BE) shifts of Fe surface and Fe nanoparticles have been analyzed by considering the bond order-length-strength (BOLS) correlation mechanism [6] in decomposition of the X-ray photoelectron spectrum (XPS). It turns out that the Fe 2p(3/2) BE shifts positively by 2.17 eV from the atomic value of 704.52 eV to the bulk value of 706.69 eV and that a further 0.32 and 0.16 eV positive shift occurs, respectively, to the top and the second atomic layers. Consistency between BOLS predictions and the measured size dependence of BE shift clarifies the dominance of the broken-bond-induced local strain and quantum trapping in perturbing the Hamiltonian and hence the positive shift of the 2p(3/2) BE of Fe surface and Fe nanostructures. (C) 2009 Elsevier B. V. All rights reserved.