The work presented here proposes a new interpretative method for thermally stimulated depolarization current (TSDC) measurements. By applying the concept of electronegativity equalization to TSDC results, we show that it is possible to obtain an experimental evaluation of the chemical potential of the electrons of the exchanged cation and of the host site in zeolites. This step leads to an evaluation of the fundamental parameters, such as the effective hardness and electronegativity of the sites of zeolites. Such an approach gives an evaluation of the heterogeneity of the aluminosilicate surface and is applied, for the first time, to an exchanged hydrogen mordenite containing various amounts of substituted Lithium ions or sodium ions. A relation betwen electronegativity and hardness and the acid-base properties of the zeolite is made possible.