Final answer:
A hydrogen ion, the symbol H+, and a hydronium ion (H3O+) are all names or symbols for the same thing in chemistry.
Step-by-step explanation:
The symbol for a hydrogen ion is H+. It is essentially a hydrogen atom that has lost its lone electron, leaving behind a single proton. In aqueous solutions, hydrogen ions tend to attach themselves to water molecules, resulting in the formation of the hydronium ion, represented as H3O+. So, H+, H3O+, and a hydrogen ion all refer to the same thing.