Re: What is the structure of N2O3?

Co-ordinate bonds are covalent bonds.  At one time it was thought that 
every pair of electrons shared between two atoms had to be composed of one 
electron from each of the atoms.  Then it was realized that there are 
cases where a shared pair seems to have come solely from one of the atoms 
sharing that pair.  This is the case with the pair shared in the single 
bond between one nitrogen atom and one oxygen atom in the Lewis structure 
of N2O3.  An oxygen atom brings 6 electrons to the Lewis structure.  The 
only way an oxygen can make a single bond and have 3 lone pairs is if the 
nitrogen has contributed the pair. So the co-ordinate covalent bond is in 
the Lewis structure which has eight electrons around all atoms.

It seems now that there is less of an attempt to draw the distinction 
between a covalent bond and a co-ordinate bond.  Add up all of the valence 
electrons and put them in the structure to fulfil the octet rule.

There is one consequence of this idea of a co-ordinate covalent bond.  The 
bond in question has charge separation. I don't know whether you have 
studied this yet, but the nitrogen atom in this bond has a Formal Charge 
of +1 and the oxygen atom in this bond has a Formal Charge of -1.  The 
molecule is still overall neutral.