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I am doing a multiple choice question for which one of the possible answers is, for the Lewis structure of NO3- (one of the oxygens is double bonded to the nitrogen and the other two are single bonded),
"one of the N-O bonds is shorter than the other two".
Apparently this is not the right answer, but my understanding was that a double bond is shorter than a single bond. I just googled it and I'm reading that the more bonds there are the shorter the bond length. So shouldn't that answer be correct?