Answer the following question given this paragraph: 

Again, the transfer of an H + ion leaves the oxidation numbers unaffected. In summary, redox reactions can always be recognized by a change in oxidation number of two of the atoms in the reaction. Any reaction in which no oxidation numbers change is not a redox reaction.


Q: Redox reactions can always be recognized by a change in what number of two of the atoms in the reaction?


A:
oxidation