What is a defining characteristic of acids?

The defining characteristic of acids is that they donate protons (H+) in solution. This behavior is rooted in the Brønsted-Lowry theory of acids and bases, which defines acids as substances that can release protons into the solution. When an acid dissolves in water, it dissociates to produce hydrogen ions. This increase in H+ concentration lowers the pH of the solution, making it more acidic.

The ability to donate protons is central to the chemical reactivity of acids and is what distinguishes them from bases, which are characterized by their ability to accept protons. This proton donation is crucial in various chemical reactions and processes, including neutralization reactions where acids react with bases.

While it is true that acids can sometimes increase the concentration of hydrogen ions to corrosion levels, this is not a universal feature of all acids, as many can be quite stable. Not all acids are corrosive, and the degree of acidity or corrosiveness depends on their concentration and chemical structure, which makes labeling all acids as corrosive misleading. Understanding that acid's primary behavior is to donate protons provides a foundational knowledge of acid-base chemistry.