What is the equilibrium constant of pure water at 25°C

K = 1.0 x 10 ⁻¹⁴ at 25º C

Explanation:

Sometimes, in pure water, one proton ( H+ion) of one water molecule will be attracted to one of the lone pairs in another water molecule.

This causes the H+ ion to leave its current water molecule (leaving behind OH−) to attach to the lone pair of another water molecule (forming H3O+, the hydronium ion).

This process is called the auto-ionization or self-ionization of water, since H2O is ionizing into OH− and H+.

They are all full and don't need any more electrons in there outer shell.