Ternary Zinc-Sodium-Phosphate glasses doped with transition metal of the composition Na2MxZn1-xP2O7(x = 0, 1, 2 and 5 mol %) (where M = Ni, Cu and Co) were prepared by the traditional quenching method. The ac conductivity measurements at different temperatures for the prepared glasses have been investigated, and the activation energy for dc conduction determined in each transition metalmetal- doped sample. The results showed that the evolution of the activation energy of the conductivity depends on the nature of the dopant ions. This surprising phenomenon, reported in many works, is not yet satisfactorily explained. A qualitative explanation is proposed, based on well-known results obtained in the study of the interactions between chemical potential of the electrons of the doped ion and of the host site in glasses, by means of density functional theory, and on the Electronegativity Equalization Method. It is shown that, when the model is applica-bleapplicable, it yields relevant information about the domi-nantdominant interactions between the glass network and the doped ion.