# Among HClO4 and HClO2 which is the stronger acid if we do not know Ka values? [duplicate]

I have two acids: $\ce{HClO4}$ and $\ce{HClO2}$ how do I determine which is the strongest acid without knowing $K_a$? The two hydrogens are bound both to an oxygen so there isn't anything to differentiate them, how can I proceed?
$\ce{HClO4}$ is stronger acid due to the formation of more stable conjugate base. Also there are more number electronegative oxygen atoms in case of $\ce{HClO4}$ , so acidity should be more.