Anytime I see any polyoxyanion I am usually thinking oxidation because you have a lot of oxygen atoms attached to one single atom. It is highly reactive in the sense it might just jump on ship with any other atom. Honestly in particular I have seen CLO3 around in some problems but I treat it as a CLO4 because they are on the same reactivity scale (applies to ClO3 and ClO4) not so much ClO2 and CLO