Trends in Acid Strength of Oxoacids

All oxoacids have the acidic H atom bonded to an 0 atom, so bond strength (length) is not a factor in their acidity, as it is with the nonmetal hydrides. Rather, two factors determine the acid strength of oxoacids the electronegativity of the central nonmetal (E) and the number of 0 atoms. 

It follows from this that HNO3 is stronger than HNO2, that H2SO4 is stronger than H2SO3, and so forth. 

A a of HOCIO2 (chloric acid) = 1 A a of HOCIO3 (perchloric acid) = 10  

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