We can look at the oxyacids of chlorine, and assign an oxidation to chlorine:
#HOCl,"hypochlorous acid", Cl(+I)#;
#HOCl(=O),"chlorous acid", Cl(+III)#;
#HOCl(=O)_2,"chloric acid", Cl(+V)#;
#HOCl(=O)_3,"perchloric acid", Cl(+VII)#.
And in general, the acid/salt with the LOWER oxidation state has an #"ous"# ending; and the acid/salt with the HIGHER oxidation state has an #"ic"# ending.
The use of #"hypo"# means #"reduced"#, here with respect to oxidation state; #"per"# means #"maximum"#. These are all old-fashioned names, and depending on your syllabus, you should not have to master them. You would, however, be required to find the oxidation state of chlorine in the oxoacid.
