Which of the following compounds does not exist?

When tin is treated with concentrated nitric acid,what is the product formed?

Which of the following oxides is least acidic?

What is the basicity of orthophosphoric acid?

Consider the following:
Statement-$I$ : $Al_2O_3$ is amphoteric in nature.
Statement-$II$ : $Tl_2O_3$ is more basic than $Ga_2O_3$.
The correct answer is

Write a note on oxidation states of group $-15$ elements. Write a note on the nature of bonding of group $-15$ elements.