Hydronium ions are composed of
OH-
H+
H2O Which one
None.
Hydronium ions are water ions attached to extra protons. We commonly write it as H30+
but in fact, these protonated water molecues exist in solution as
H3O+
H9O4+
H4O2+
So what is happening in water. A few water molecules dissociate into H+ and OH, but because the H+ is an isolated proton, it cannot exist by itself. It is solvenated by surrounding water molecules, forming these clumps of water molecules "charged". WE call these hydronium.