The oxidation number of Cl in HClO₄ is

Question

The oxidation number of Cl in HClO₄ is ?

Answer 1

HClO₄ has no net charge, so the oxidation numbers of the elements must add to zero,

H is 1+

O is 2- and there are 4 of them for a total of 8-

What does Cl have to be so that the sum is zero?

It has to be 7+, so that is the oxidation number of Cl in HClO₄