Question

Please help, I am asked: Which has the larger N–O bond length, NO2– or NO3–? and why?

I have determined the lewis structure for the two molecules but I do not know how to tell which has the larger N-O bond length and why.

thanks...

Answer 1

NO3-

Okay if you look at the structure of NO3- you'll notice that N makes 1 double bond and 2 single bonds. Thus because of hybridization, you can say each oxygen atom has 1/3 of a double bond on average.

Now look at NO2- (O=N-O-). There is one double bond and one single bond. Since each oxygen atom has about 1/2 of a double bond, the average bond length will be shorter than those in NO3-.