Question

How would one work out the oxidation number or Chlorine in `NH_4ClO_4`?

Answer 1

The oxidation number of chlorine in perchlorate is `VII+`.

Explanation:

Chlorine achieves its maximum oxidation number in perchlorate, i.e. `Cl(VII+)`.

How did I find the oxidation number? Well, the oxidation number of oxygen in oxides is typically `-II`, and it is here. The sum of the oxidation numbers is the charge on the ion, here `-1`. And thus, `-1=4xx(-2)+Cl_("ON")`. Capisce?

What is the oxidation state of `Cl` in `ClO_3^(-)" , chlorate ion?"`.

As a matter of interest, ammonium perchlorate is a prohibited substance. It is a potent oxidant, and would cause police officers to have kittens.