Final answer:
The hydronium ion, represented as H3O+, is a hydrogen ion H+ attached to a water molecule, essential in the study of solution chemistry.
Step-by-step explanation:
The hydronium ion, denoted as H3O+, is essentially a hydrogen ion (H+) that is associated with a water molecule. Essentially, when a hydrogen ion is in an aqueous solution, it's not just a bare proton; it forms a hydronium ion by attaching to a water molecule. These ions are crucial in understanding the chemical properties of solutions, especially regarding their acidity or basicity.