Number of amphoteric compounds among the following is

$\mathrm{BeO},\mathrm{BaO},\mathrm{Be}\left(\mathrm{OH}{)}_2\text{ and }\mathrm{Ba}\right(\mathrm{OH}{)}_2$

Beryllium forms amphoteric oxide due to its small size and high electronegativity.

And Barium forms basic oxide and hydroxide due to its high electropositivity or metallic character.’

Thus, BeO and $Be{\left(OH\right)}_2$ are amphoteric in nature, and BaO and $Be{\left(OH\right)}_2$ are basic in nature.

Hence, the number of amphoteric compounds among the following is 2.