Lewis structure of NO2- ion is drawn in this tutorial. Total valence electrons of nitrogen and oxygen atoms and negative charge also should be considered in the drawing of NO2- lewis structure.
Now, we are going to learn, how to draw this lewis structure.
Following steps are required to draw NO2- lewis structure and they are explained in detail in this tutorial.
Drawing correct lewis structure is important to draw resonance structures.
There are one nitrogen atom and two oxygen atoms in the nitrate ion. Also there is a -1 charge.
Nitrogen and oxygen are located at VA and VIA groups respectively in the periodic table. So nitrogen has five electrons in its valence shell. In oxygen atom, there are six electrons in its valence shell.
There are two oxygen atoms in NO2, Therefore
Due to -1 charge, another electrons is added
Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells
Total electron pairs are determined by dividing the number total valence electrons by two. For, NO2-, there are 18 valence electrons pairs, so total pairs of electrons are 9.
To be the center atom, ability of having greater valance is important. Therefore nitrogen has the more chance to be the center atom (See the figure). So, now we can build a sketch of NO2- ion.
There are already two N-O bonds in the sketch. Therefore only seven valence electrons pairs are remaining.
Start to mark those seven valence electrons pairs on outside atoms (oxygen atoms) as lone pairs. One oxygen atom will take three lone pairs following the octal rule (oxygen and nitrogen atoms cannot keep more than eight electrons in their valence shells).
Two oxygen atoms will take six valence electrons pairs. Now one valence electrons pair is remaining. Mark that remaining one on nitrogen atom.
The drawn structure for NO2- is not a stable one because both oxygen atoms and nitrogen atoms have charges.
Now, we should try to minimize charges by converting lone pair(s) which exist on oxygen atoms to bonds. So we convert one lone pair of one oxygen atom as a N-H bond.
Now there is a double bond between nitrogen and one oxygen atom. There is a single bond also with nitrogen atom and other oxygen atom.
In new structure, charges of atoms reduced. Now there is no any charge on one oxygen atom and nitrogen atom. Now you understand this structure of NO2- is more stable than previous structure due to less charges.
We cannot convert more lone pairs of other oxygen atom to make a bond with nitrogen atom because nitrogen cannot keep more than eight electrons in its last valence shell.