An Arrhenius acid is that of any substance that ionizes when it dissolves in water to give the H+ or hydrogen ion. An Arrhenius base is any substance that gives the OH–, or hydroxide, ion when it dissolves in water.
- Acids provide the H+ ion; bases provide the OH– ion, and these ions combine to form water.
In 1923, chemists Johannes Nicolaus Brønsted and Thomas Martin Lowry independently developed definitions of acids and bases based on the compounds’ abilities to either donate or accept protons (H+ ions).
- In this theory, acids are defined as proton donors, whereas bases are defined as proton acceptors.
- A compound that acts as both a Brønsted-Lowry acid and base together is called amphoteric.