We addressed in this study the process of specific adsorption of anions at the metal/solution interface; We focused on the nature of the surface chemical bond that accounted for the phenomenon of adsorption specificity in the context of bisulfate coverage and structural information. While we limited our investigations to bisulfate adsorption on the Pt(111) electrode in sulfuric and mixed sulfuric/perchloric acid media, our conclusions have general significance in explaining ionic adsorption events in electrochemistry. We used core-level electron energy loss spectroscopy, auger electron spectroscopy, low energy electron diffraction, and cyclic voltammetry. Our findings show that in the studied range of sulfuric acid concentration (10(-4)-10(-1) M) the maximum anion coverage is 0.34 +/- 0.02 monolayer (ML) and that this coverage corresponds to a highly ordered Pt(111)(root 3 x root 3)R30 degrees surface structure. S2p core-level and LMM Auger electron spectra indicate that the chemical state of bisulfate sulfur is +6, as in the sulfate anion ina sulfate salt matrix. However, the electron density on the adlattice sulfur is higher than in the salt, evidently due to back-donation of electrons from the substrate to the adsorbate. We conclude that backdonation plays a major role in binding the anions to the surface. Further, the plot of the back-donated electron density vs electrode potential assumes a distorted parabolic shape, The descending parabola branch covers the potential range where bisulfate adsorption increases with potential, and a flat minimum coincides with the double layer potential range. When OH adsorption and platinum oxidation begin, a 2D compressive effect of the O-type adsorbates causes the bisulfate-platinum O-Pt bond to besequentially cleaved. The "flow" of metal electrons to the adsorbate is therefore reduced, and the S2p loss energy approaches the level characteristic of sodium sulfate unperturbed by surface interactions. Loss spectra from Pt4f(7/2) confirm that the oxidized surface is emersed to vacuum but in the double layer potential range fail to respond to either the electrode potential change or the bisulfate adsorption.