Hydronium ion formation

Definition

A free hydrogen ion does not remain alone in water; it immediately bonds to a neighboring water molecule to form hydronium. This is written H+ plus H2O gives H3O+.

Because a bare hydrogen ion is just a proton with no electron cloud, it is extremely reactive and grabs the nearest water molecule instantly. The resulting positive charge does not stay in one place but hands off from molecule to molecule. Writing self-ionization as 2 H2O reversibly equals H3O+ plus OH- accounts honestly for this hydration.

Related concepts

Grotthuss proton hopping · Self-ionization of water · Hydrogen ion as bare proton

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Part of The Blueprint of Water · 🧪 chemistry