* Hydronium ion (H3O+)

* Hydroxide ion (OH-)

The dissociation of water is a reversible reaction, represented by the following equation:

2H₂O ⇌ H₃O⁺ + OH⁻

This means that water molecules are constantly breaking apart and reforming. The concentration of hydronium and hydroxide ions in pure water is equal, resulting in a neutral pH of 7.