Hydronium

Hydronium is a common Polyatomic Ion. Its Chemical formula is $H_{3}O^{+}$.

Hydronium is present in all aqueous solutions, as the acidic counterpart to the alkaline hydroxide ($OH^{-}$). A hydronium ion will combine with a hydroxide ion to create two water ($H_{2}O$) molecules. An imbalance will shift the pH down if hydronium is more dominant.