text: when the electrostatic interaction between the ions increases the ionic strength increases. It is not just the presence of ions that effects the ionic strength. \n\nThe interaction should also be there. for interaction, further study of polar and difference in Electronegativity comes into picture. So it is not just the presence. and the number which effects the ionic strength. \n\nBut for pH the number matters. the number of hydrogen ions H+ and OH- ions matters which effects the pH.\n\nHope that was clear enough.\nAny doubts u can ask further.