Dinitrogen pentoxide is an strong acidic oxide and nitrogen atom is at +5 oxidation state. Here we are going to draw lewis structure and resonance structures of N2O5 molecule.
Sketch of N2O5 molecule is below. We are going to find, how σ bonds, π bonds and lone pairs are located in this molecule.
Now, we start to draw the lewis structure. In the given sketch, five σ bonds have already marked. So there are 15 remaining electrons pairs. Then mark rest of electrons pairs as lone pairs on oxygen atoms. See the following figure.
Octet of two nitrogen atoms are incomplete. Therefore this structure is wrong and we have to change bonds and lone pairs of atoms as nitrogen gets its octet state.
Charges are spread all over in drawn molecule. So this is not stable and we have to reduce charges on atoms by transferring lone pairs to bonds.
Both nitrogen atoms have +1 charge and two oxygen atoms have -1 charges. Octet of each atoms is complete. We take the most stable structure as our lewis structure.
Lone pairs and bonds of atoms are exchanged to obtain new structure. You can see arrows which transform lone pairs to bonds or bonds to lone pair.
According to the charge spreading, stability of molecule is expressed relatively.
A structure is unstable, if oxygen atom hold a positive charge because oxygen's electronegativity is higher than nitrogen atom. Therefore nitrogen atom should hold the positive charge when there are only nitrogen and oxygen atoms.
You can draw more resonance structures by following these steps and find whether they are stable or not.
N2O5 molecule does not have a charge. But its atoms have charges on them and summation of those charges is 0.
Both nitrogen atoms are at their highest oxidation state, +5 in N2O5 molecule.