Illustrated Glossary of Organic Chemistry

Hydronium ion: H₃O⁺. A strong acid; pK_a = -1.8. The conjugate acid of water. Frequently (and somewhat incorrectly) written as H⁺ (i.e., a naked proton).

Molecular Structure of Hydronium Ion

Lewis structure		Ball and spoke model		Space-filling model		Molecular model kit