Question

How many covalent bonds occur in the `N_2O_5` molecule?

Answer 1

Well, I count 8 bonds all together.......

Explanation:

A simple vesper treatment of `N_2O_5` must distribute `5xx6+2xx5` `=20*"electron pairs"` across 7 centres......

`""^(-)O(O=)stackrel(+)N-O-stackrel(+)N(=O)O^-`

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 `"nitrate ion..."`, `O=stackrel+N(-O^(-))_2`. What is the formal charge on this ion?