Acids and Bases Definitions


The most common definitions of acids and bases are Arrhenius acids and bases, Brønsted-Lowry acids and bases, and Lewis acids and bases. 

Brønsted-Lowry acids and bases
  • A Brønsted-Lowry base is a substance that accepts hydrogen ions during a chemical reaction. (Bases are proton acceptors)
  • A Brønsted-Lowry acid is a substance that gives up hydrogen ions during a chemical reaction. (Acids are proton donors)

Arrhenius acids and bases
  • An Arrhenius acid is a substance that when added to water increases the number of H+ ions in the water. Acid + H2O → H3O+ + conjugate base
  • An Arrhenius base is a substance that when added to water increases the number of OH- ions in the water. Base + H2O → conjugate acid + OH-

Lewis acids and bases
  • A Lewis acid is a substance that is an electron pair acceptor.
  • A Lewis base is a substance that is an electron pair donator.