How many covalent bonds occur in the #N_2O_5# molecule?
Well, I count 8 bonds all together.......
A simple vesper treatment of
And the given Lewis structure does distribute these electron pairs....does it not? The nitrogen centres are formally quaternized with only 4 electrons associated with the nitrogen centres, i.e. entailing a formal positive charge on each nitrogen atom, and the formally singly bound, terminal oxygen have a corresponding formal negative charge. Of course, these formal charges are delocalized by resonance.
For another example of this consider