* Hydrogen ions (H+)

* Hydroxide ions (OH-)

These ions are formed through the auto-ionization of water, where a water molecule donates a proton (H+) to another water molecule:

H₂O + H₂O ⇌ H₃O⁺ + OH⁻

The hydronium ion (H₃O⁺) is often simplified to H+ for ease of representation.

While pure water contains both H+ and OH- ions, it is important to note that the concentration of each ion is extremely low, making pure water neutral.