Amphoteric Compounds other than Be, Al, Ga, Sn, Pb, and Sb

[Kate Osborne 1H]

I understand that Be, Al, Ga, Sn, Pb, and Sb form amphoteric compounds but how do we tell for other compounds? I know that H2O is amphoteric but it doesn't have any of these elements so how do we tell for other compounds?

[Aman Sankineni 2L]

The definition of amphoteric is a species that is able to act as both a base and acid, which means it should be able to accept and donate a proton when need be. The easiest way to remember is if the elements in question are part of the metalloid oxides section of the periodic table as opposed to the nonmetal oxides (group p) which are acidic and the metal oxides (group 1 and 2) that are basic

[Goyama_2A]

I don’t think there is any set steps to determining whether or not something is amphoteric. However, it is helpful to think about the conjugate base and/or acid of something in determine whether it is amphoteric. If something doesn’t have a Hydrogen atom, it obviously doesn’t have a proton to donate and therefore couldn’t act as an acid. Subsequently, if something is unable to hold any more atoms, it can’t accept protons and therefore cannot be a base. Water is amphoteric because it can both accept a proton to become H3O or lose one to become OH-. Something like NH4+ on the other hand isn’t amphoteric because, although it can lose a proton to become NH3, it cannot take in another hydrogen, and therefore cannot act as a base.

[Aadil Rehan 1D]

Good ways to check if something is amphoteric:
- Does it have at least 1 hydrogen to donate?
- Is it negative or neutral? (more likely to allow a hydrogen to bond)
- Does it have lone pairs / can it form another bond?