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There was a question on the midterm about determining the bond length for N-O in NO2, given that the a single bond is 140Å(?) and a double bond is 120Å(?) (I don’t quite remember the units). Any clue on how to determine that?
I believe that the Lewis structure for NO2 has one single bond and one double bond. So, in nature, this double bond would be evenly distributed between the two, so I assumed the each bond would be approximately a "1.5" bond. Using this logic, I guessed that the bond length would be about 130A.
For the question that came this one, did people say that the bond length was the same for all the structures since they are resonance structures? (the bond lengths for the most stable structure of the compound?)
Since a resonance hybrid is a blend of Lewis structures, all the bond lengths are the same. Thus, even though there are both single and double bonds in the resonance structure, all of the bond lengths will be the average between the different bond lengths of the structure. For this specific question, this would be 130.
During lecture Lavelle gave us the experimental value for the average bond length in Nitrate, which turned out to be 1.24 A, maybe because when you draw the three possible structures for NO3-, there are two single bonds and one double bond. That being said, I think the correct answer on the midterm was 130 A.
There were resonance structures for the molecule that included single and double bonds, so the actual molecule would have an average of those two bonds. I took the average of the two lengths and got 130pm.
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