State reasons for each of the following:
The N-O bond in is shorter than the N-O bond in
The shorter N - O bond in is due to the existence of resonance in. The resonating structures can be drawn as follows.
Due to resonance in, the two bonds are equivalent. This leads to a decrease in bond length.
Thus, the N - O bond length in resembles a double bond.
Now, the resonating structures for can be drawn as:
As seen from the above resonating structures of 
, the three oxygen atoms are sharing two single bonds and one double bond. So, the real N - O bond length resembles a single bond closely.
In 
the lone pair is delocalized between the 2 oxygen groups. Bond order equal to 1+1/2=3/2.
In 
lone pair shared between three oxygen atom hence bond order =1+1/3=4/3.
Greater the bond order shorter the bond. Hence bond length of 
less than that of 
This explains the existence of shorter bond length of the N - O bond 
in than in 
.
