The effect of solvent on the electronegativity, hardness, and condensed Fukui function, and atomic softness for a set of diatomic and small polyatomic molecules and ions has been studied using the effective fragment potential (EFP) model. The binding function was used for monitoring the solvation of the molecule. We do not observe a decrease in the HOMO-LUMO gap in the solvent, All anions show a significant change in the chemical potential. Both HOMO and LUMO energy levels decrease in the solvent phase as compared to the gas phase. For the major part of the acids, the increase in the LUMO orbital energy is larger than in the HOMO orbital energy. For the group of salts, we observe an increase in the LUMO energy level and a similar decrease in the HOMO energy level, resulting in a small change in the chemical potential. The importance of the change in the wave function upon solvation was shown through an analysis of the relaxation part in the hardness and condensed Fukui function. Very close values found for the same ions in molecules such as LiH, LiF, NaH, NaF, and LiF indicate that in these cases very good separated ion pairs are present.