balance the following redox reaction by oxidation number method: Zn + HNO3 --> Zn(NO3)2 + NO + H20. Answer: 1. The zinc atoms are changing their oxidation number from 0 to +2, and some of the nitrogen atoms are changing from +5 to +2. in Zn(NO3) 2 , the oxidation number of only Zn is +2