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On the periodic table, there is an anomaly in the ionization energy trend, in which Oxygen has "lower" IE than Nitrogen due to the fact that the oxygen has electron repulsion in its 2p orbital from the added electron pair, and nitrogen doesn't. So in this case, the increase in the effective nuclear charge of the oxygen cannot negate the repulsion induced by the electron pair, and hence, it is easier to remove an electron from the Oxygen than it is from the Nitrogen. If Oxygen has the lower ionization energy than Nitrogen though, then why in NNO is the nitrogen placed in the center, instead of the oxygen? It would make sense to place the oxygen in the center, since that would be more energetically feasible, since it would be sharing the most electrons in the compound, and having the lower ionization energy would facilitate that. So, why isn't Oxygen in the center of NNO?
Regarding your question, sometimes I don't think you need to look at Lewis structures so technically. Nitrogen is in the middle of the molecule because it can form more bonds and also you might need to take a look at the formal charges to determine this. However, this is one of the few exceptions to Lewis structures where the lone atom is not in the middle. Also, the outer atoms are often more electronegative. I hope this helped!
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