How To Tell Which Compounds are Amphoteric?

[Nancy Li 1C]

Is there an easy way to identify which compounds are amphoteric? Or should we just be memorizing common amphoteric substances?

[Mona Reddy Kurra 1J]

Hi! I think one way to determine whether a compound is amphoteric is to see whether it can accept and donate protons, or hydrogen ions. If a compound can do both, then it acts as both an acid and base, so it is amphoteric. For example, can donate the H+ to become or it can accept an H+ to become . I hope that helps!

[AudreyQian1J]

Hello,
One way that could help to identify amphoteric substances is to look for the ability to both add and remove H+ ions from a molecule. In other words, you can look for whether the substance contains more than one H+ ions or multiple charges on its cation or anion. For example, H2PO4- is an amphoteric substance, because removing a hydrogen ion would produce HPO42- + H3O+ and adding a hydrogen ion would produce H3PO4 + OH-. H2PO4- has both hydrogen and a negative charge, producing conjugate acid H3PO4 and conjugate base HPO42-.
Another way is to look at the periodic table, where there is a diagonal band of amphoteric oxides, found in between metal oxides (bases) and nonmetal oxides (acids), that closely matches the diagonal band of metalloids.