Assign an oxidation number to each elementary in the following compounds or ions N2O5

Oxidation number per Nitrogen + 5, oxidation number per Oxygen - 2

Explanation:

So we know that oxidation number of Oxygen is - 2 so we have - 2x5 = - 10 charge. This gives a total oxidation number charge of - 10 for the five oxygen atoms in N2O5. To maintain electrical neutrality, as required for all compounds, the two nitrogen atoms must have a total oxidation charge of + 10, so that each of the two nitrogen atoms has an oxidation number of + 5