Answer : The formal charge on nitrogen atom is Zero (0).
Explanation :
Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.
In the Lewis-dot structure the valance electrons are shown by 'dot'.
The given molecule is, [tex]CN^-[/tex]
As we know that carbon has '4' valence electrons and nitrogen has '5' valence electrons.
Therefore, the total number of valence electrons in [tex]CN^-[/tex] = 4 + 5 + 1 = 10
According to Lewis-dot structure, there are 6 number of bonding electrons and 4 number of non-bonding electrons.
Now we have to determine the formal charge for each atom.
Formula for formal charge :
[tex]\text{Formal charge}=\text{Valence electrons}-\text{Non-bonding electrons}-\frac{\text{Bonding electrons}}{2}[/tex]
[tex]\text{Formal charge on C}=4-2-\frac{6}{2}=-1[/tex]
[tex]\text{Formal charge on N}=5-2-\frac{6}{2}=0[/tex]
Hence, the formal charge on nitrogen atom is Zero (0).
