The lewis structure of Nitrile Ion is drawn as,
Step 1) Add all the valence electrons of each element present in molecular ion.
Valence Electrons of N = 5
Valence Electrons of O₁ = 6
Valence Electrons of O₂ = 6
One electron for negative charge = 1
-------------
Total valence electrons 18
Step 2: Draw the Nitrogen atom as central atom surrounded by oxygen atoms. Now connect central atom with oxygen atoms via single bonds and subtract two electrons per single bond from total valence electrons . i.e.
18
- 4
-------
14
Divide these 14 electrons on each element starting from most electronegative atom to complete its octet. A single lone pair will diminish on formation of the second bond.
The lewis structure of Nitrilte ion with two isomeric forms is given below, each element is given a single colour to show that the nuclei position remains the same during resonance.
