Binary oxides can be clarified as acidic, basic, or amphoteric based on their chemical properties. The general trend is that the oxides with elements in the lower left side of the periodic table are more basic than the elements in the upper right corner. A numeric scale of acidity and basicity was calculated by D.W. Smith based on thermochemical data for oxoacid salts with H 2 O as the reference . The scale provides a quantitative comparison between different oxides and has been used for explaining different surface and bulk behavior for various oxides . Recent findings revealed a strong relation between the oxygen exchange kinetics and the relative acidity in Smith scale . This relationship provided a reasonable explanation for the different catalytic performances of various cathode materials investigated for Solid Oxide Fuel Cells (SOFCs) and inspired new materials development.