# How do we know if a compound is amphoteric or not?

My teacher told me if it reacts with an acid and a base, then the compound is amphoteric.

However, I am not satisfied. Is there any other way of telling? For example we are give a compound say BeO, how can we say if it's amphoteric or not?

• Examine the structure? Do you mean, experimentally? – Buck Thorn Jun 16 '19 at 19:40
• socratic.org/questions/…  If the substance can act like both an acid and a base, i.e., both give and accept protons, then it's amphoteric. – Christopher Marley Jun 16 '19 at 19:41
• Sorry to tell you but your teacher's opinion is not right, just because the "react" is not enough. You may say that if an oxide reacts with an acid and forms a salt or if an oxide reacts with a base forms a salt then you can say that it is an amphoteric oxide. Take an example of aluminum oxide, when dissolved in HCl it will form aluminium chloride, but we can also dissolve it in NaOH, where it forms sodium aluminate. – M. Farooq Jun 16 '19 at 22:03

2) Notice I say "metal" above. Nonmetals generally form oxides that are only acidic ($$\ce{CO2}, \ce{SO2}$$) or inert ($$\ce{CO}, \ce{NO}$$). You need a metal for the oxide to react with water or acid as a base would.