Amphoteric Character of Partially Deprotonated Acids

[Ingrid Wu 1I]

I understand that a partially deprotonated acid like H2PO4- can act as an amphoteric substance by both donating/accepting protons/electrons depending on environmental conditions, but I also know that as more protons are removed from the phosphate ion, it will "hold on" to the remaining protons more tightly as a result, as exemplified by the successively lower and lower equilibrium concentrations of more completely deprotonated species. Is there a point along this scale at which the partially deprotonated acid loses its amphoteric character? Obviously, when completely deprotonated (PO4-3) it would only be able to act as a base, but I was thinking something like HPO4-2.

[Wendy Phung]

In the case of HPO4-2, the partially deprotonated acid does not lose its amphoteric characteristic, rather the compound displays weaker acid characteristics as the remaining protons are tightly bonded. Therefore, in HPO4-2, it would be less favorable for the compound to donate protons, meaning that it would still maintain its acidic properties but to a lesser degree.