We studied the specific effects of NaCl, KCl, MgCl₂ and CaCl₂ on the ability of sodium dodecyl sulfate (SDS) to inhibit the coalescence of the bubbles in water and to make foam. We related our observations with the thermodynamic data about the activities of the salts and water using the model of Pitzer for each particular salt. Moreover, we measured the surface tension of each particular foaming solution, which allowed us to calculate the adsoprtion parameters of SDS in the presence of the different salts. All these allowed us to look at our main experimental data from different perspectives. As we have expected, the addition of each one of the salts to the aqueous solution of SDS significantly decreased its critical coalescence concentration (CCC). Yet their effects on the ability of SDS to make foam were various. For example, NaCl significantly increases the foaming ability of SDS, while KCl acts as foam suppressor. MgCl₂ boosts the ability of SDS to make foam, while CaCl₂ appears to be foam suppressor. Sodium (Na) and Potassium (K) belong to the 1A group of the Mendeleev’s periodic table, while magnesium (Mg) and calcium (Ca) belong to the 2A group. Sodium (Na) is a foam booster, while potassium (K) is a foam suppressor. Magnesium (Mg) is a foam booster while calcium (Ca) is a foam suppressor. The two pairs of chemical elements have identical electronic configurations in their last electronic layers. The only difference between them is in the radii of their atoms. This difference draws difference in their ionization potentials, polarizabilities, hydration numbers and all related thermodynamic parameters. We developed a detailed analysis, thus drawing the conclusion that the larger counter-ions act as flocculants of the surfactants, thus becoming foam suppressors, while the smaller ions act as foam boosters.