The Hydronium Ion

The Hydronium ion is result of the combination of a water molecule and a proton. The proton most commonly comes from a Hydrogen atom that has lost its single electron. These come from ionized acid molecules, such as Hydrochloric acid.

When the HCl molecule encounters water it ionizes to give a proton, H+, and a Chloride ion (Cl-). The proton is not left floating freely, however. Each water molecule consists of two Hydrogen atoms covalently bonded to one Oxygen atom. Each water molecule has two unbound electron pairs, called lone pairs.

While this is more stable than the Hydrogen-Chlorine bond in HCl, it is still highly reactive. The proton has a strong tendency to break away from the H3O+ ion and either combine with other elements to form new compounds, or if it is in the presence of a metal it tends to steal electrons from the metal to form Hydrogen gas.

This last reaction causes loss of electrons from the metal lattice which results in corrosion of the lattice. The imbalance in positive and negative charges in the metal lattice causes positive metal ions to drop off until the balance in the metal lattice is restored. This is addressed further in the what is rust? page.

The corrosion of metals by acid is fundamental to the operation of batteries, which are an integral part of any stand-alone or batter-backup solar power system.