In ammonium nitrate NH4NO3 , there are two nitrogen atoms with different oxidation states. In the ammonium ion NH4+ , the nitrogen atom is bonded to four hydrogen atoms. Hydrogen has an oxidation state of +1. Therefore, the oxidation state of nitrogen in NH4+ is -3 to balance the overall charge of the ion.In the nitrate ion NO3- , the nitrogen atom is bonded to three oxygen atoms. Oxygen has an oxidation state of -2. The overall charge of the nitrate ion is -1. Therefore, the oxidation state of nitrogen in NO3- is +5.So, in ammonium nitrate, the oxidation states of nitrogen are -3 in NH4+ and +5 in NO3- .