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Hydronium ion

H3O+H_3O^+

Charge: 1+ · Type: Polyatomic cation · Molar mass: 19.023 g/mol

Made of: hydrogen, oxygen

How it forms

When an acid dissolves in water, its proton transfers to a water molecule to form H3O+. Chemists often write H+ for simplicity, but hydronium is the real species present.

Naming note

H3O+ is the hydronium ion, also called oxonium. In equations it is interchangeable with H+(aq), which is shorthand for the same thing.

Examples in compounds

  • Hydrochloric acid solution

  • Sulfuric acid solution

  • Nitric acid solution

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