What is hydronium?
Hydronium is a cation, composed of one proton and no electrons. The name hydronium is given to this species when it is solvated in water, forming the hydronium ion H3O+.
The definition of an acid
An acid is a molecule or ion capable of donating a hydron, or, alternatively, capable of forming a covalent bond with an electron pair (a Lewis acid). The first category of acids is the proton donors or Brønsted acids. In the special case of aqueous solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents. A Brønsted or Arrhenius acid usually contains at least one hydrogen atom bonded to a very electronegative atom such as chlorine, bromine, or sulfur. Any compound that donates protons is an acid.
The second category of acids are Lewis acids, which form a covalent bond with an electron pair. Unlike Brønsted and Arrhenius acids, Lewis acids do not necessarily contain hydro- gen atoms. For example, boron trifluoride (BF3) is frequently used as a Lewis acid in organic synthesis even though it does not have any hydrogen atoms. In general, any compound that can accept an electron pair from another molecule is called a Lewis acid. In water, the hydroxide ion (OH-) acts as a Lewis base by donate ing an electron pair to H 3O+.
The definition of a base
A base is a substance that can accept hydrogen ions. Hydronium is a molecule that consists of a hydrogen ion and two electrons. Therefore, it cannot accept any more hydrogen ions, and it is not a base.
Hydronium’s place on the pH scale
Hydronium is considered to be a strong acid, and as such, it has a pH of 0.
The difference between an acid and a base
The difference between an acid and a base is the concentration of hydrogen ions in solution. An acid is a molecule that donates hydrogen ions, while a base is a molecule that accepts hydrogen ions. The more hydrogen ions in solution, the more acidic the solution will be.