Pd is an important constituent in topological insulators with pronounced energy states pertaining to undercoordinated surface and edge atoms but the physical origin of these excessive states remains unclear.Here we show that consistency between Density Functional Theory calculations and photoelectron spectroscopy measurements confirmed our theoretical predications on the 5d core level shift of Pb skins and clusters.It is clarified that the shorter and stronger bonds between under-coordinated atoms cause local densification and entrapment of the core electrons, which polarize the otherwise conducting electrons in the skins and edges, which results in the electron binding-energy shift of the skins and clusters.Numerical analysis turns out that the 5d5/2 level shifts from the value of 18.283 eV for an isolated Pb atom by 3.478 eV upon bulk formation.Meanwhile, this approach has enabled us to determine the local bond length, bond energy, binding energy density, and atomic cohesive energy at the undercoordinated atomic sites.