Which ion is responsible for the acidic properties of acids?

Acids show their acidic nature because they release hydrogen ions (H+) when mixed with water. These H+ ions are what make a solution acidic. The more H+ ions there are in a solution, the stronger the acid is. H+ ions are also called protons, and they can join with water molecules to form hydronium ions (H3O+). We use the pH scale to measure how acidic or basic a solution is. A lower pH means there are more H+ ions, which means the solution is more acidic.