Here's why:

* pH scale: The pH scale measures the acidity or alkalinity of a solution. It ranges from 0 to 14, with 0 being the most acidic and 14 being the most alkaline.

* H+ ions: Acidity is determined by the concentration of hydrogen ions (H+) in a solution.

* The relationship: The pH scale is logarithmic, meaning each whole number change in pH represents a tenfold change in H+ concentration.

So, a low pH (e.g., 2) means there are a lot more H+ ions present than a higher pH (e.g., 7).

In simpler terms: The lower the pH, the "stronger" the acid, and the more hydrogen ions (H+) are floating around in the solution.