WHY The oxides in higher oxidation states of group 15 elements are more acidic than that of lower oxidation state
11Since, the higher oxidation states tend to come back to the lower oxidation states, their acidic character is strong.......This effect is more pronounced in the lower gorup members like Bismuth [4]
DON'T KNOW IF IT IS RIGHT, BUT THAT'S MY BEST SHOT [1]
1higher oxidation states are formed by loosing electrons from stable d/p/s orbitals.hence they tend 2 fill thier orbitals so that they become stable..hence their acidic nature is more..