The speciation diagram obtained using these pK values shows three distinct regions. In effect, H
3PO
4, H
2PO−
4 and HPO2−
4 behave as separate weak acids. This is because the successive pK values differ by more than 4. For each acid, the pH at half-neutralization is equal to the pK value of the acid. The region in which the acid is in equilibrium with its conjugate base is defined by pH ≈ pK ± 2. Thus, the three pH regions are approximately 0–4, 5–9 and 10–14. This is idealized, as it assumes constant ionic strength, which will not hold in reality at very low and very high pH values.