@rrusciguy In the USA you are incorrect. You may be confused because Tritium is an Isotope of hydrogen, and is written with a superscript (3). Tritium oxide is ³H2O The 3 in the top corner represents the fact that hydrogen has an atomic weight of 3. (It also has an atomic number of 1) Tritium is an isotope of hydrogen. H3O is generally formed when an acid is dissolved in water, and ions are formed. for example in HCl acid, in water you would get H30 ions and Cl ions. (H3O is hydronium)
(the silly forum won't let me put a little two or three to the bottom right of the letter)