he ion H3O+, consisting of a protonated water molecule and present in all aqueous acids.
In chemistry, hydronium is the common name for the aqueous cation H3O+, the type of oxonium ion produced by protonation of water. It is the positive ion present when an Arrhenius acid is dissolved in water, as Arrhenius acid molecules in solution give up a proton to the surrounding water molecules.
What is a hydronium ion? *