Cyanide Ion (CN–) Formal Charge
In the cyanide ion (CN–), the carbon (C) atom shares a triple covalent bond with the nitrogen (N) atom. Its Lewis structure is shown below.
Let us calculate the formal charge of the CN– molecule by determining the formal charges on C and N.
V = 4, N = 2, B = 6
Therefore, formal charge on carbon is given by,
qf = 4 – 2 – 6/2 = -1
The formal charge on C in CN–is -1.
V = 5, N = 2, B = 6
Therefore, formal charge on nitrogen is given by,
qf = 5 – 2 – 6/2 = 0
The formal charge on N in CN– is zero.
The net formal charge is: -1 + 0 = -1
The formal charge of cyanide ion is -1.