Question

Why is B2O3 acidic while al2O3 is amphoteric?

Answer 1

boron trioxide i.e., b2o3 is an anhydride(when reacted with water, it becomes​ boric acid) of boric acid I.e., b(oh)3 or h3bo3. Hence, it is said to be acidic.
But, in the case of aluminium, since it is a metalloid( neither exactly a metal nor a non metal) and has decreased non metallic properties compared to boron, the oxide of aluminium is amphoteric( neither acidic nor basic) in nature.
As we go down the elements in the boron row, the oxides of other elements like gallium, indium, thallium are basic in nature...

Answer 2

Answer:

:

b2o3 is an anhydride(when reacted with water, it becomes​ boric acid) of boric acid I.e., b(oh)3 or h3bo3. Hence, it is said to be acidic.

But, in the case of aluminium, since it is a metalloid( neither exactly a metal nor a non metal) and has decreased non metallic properties compared to boron, the oxide of aluminium is amphoteric( neither acidic nor basic) in nature.