Resonance structure of nitrous oxide

[semc]

I was asked to draw the resonance structure of nitrous oxide and given some bond length. So i need to eliminate non-probable resonance structure for nitrous oxide. I was able to draw three structure but how do we use the bond length to liminate non-probable resonance structure for nitrous oxide?

 

[sjb-2812]

I was asked to draw the resonance structure of nitrous oxide and given some bond length. So i need to eliminate non-probable resonance structure for nitrous oxide. I was able to draw three structure but how do we use the bond length to liminate non-probable resonance structure for nitrous oxide?

Which are the three structures that you have? Perhaps take a look at a similar question at http://www.chemicalforums.com/index.php?topic=37405.0 ?