Determine the oxidation states of the elements in the compounds listed. None of the oxygen-containing compounds are peroxides or superoxide.

(a) H3PO4

(b) Al (OH) 3

(c) SeO2

(d) KNO2

(e) In2S3

(f) P4O6

You need to remember that the oxidation number of H is + 1, except when it is in a metal hydrites like NaH, where its oxidation number is - 1. Then, the oxidation number of O is - 2, but in peroxides is - 1. So with these rules you just have to multiply the ox. number with the name of atoms and all the elements in the reaction must sum 0.