Groups 1 and 2 cations + halogens

[Aaina 2D]

Hi! Why don’t groups 1 and 2 cations or halogens have an effect on the pH of the solution?

[Chem_Mod]

Everything is verified experimentally in chemistry, so, in short, when researchers dissolved those substances in water, they found nothing happened to the pH.
More conceptually, halogens, except F-, are the conjugate bases of strong acids like HCl, HBr, HI. The stronger the acid, the weaker the conjugate base because equilibrium highly favors dissociation into H+ and X- rather than reformation of HX from H+ and X-. So if you have a really strong acid, it's base will be so weak that it is basically inert in water.
For the Group 1 and 2 metal cations, remember they are commonly used as salts with OH- or O2- to act as bases, ie adding NaOH in water makes it very basic. The OH- increases the pH, and we use the Group 1/2 metal cation because it does nothing in water