Question

a student proposes the following lewis structure for the isocyanate (nco^-) ion.
:c\equiv o - \ddot{n}: ^-
assign a formal charge to each atom in the students lewis structure.

Explanation:

Step1: Recall the formula for formal charge

The formula for formal charge is \( FC = V - N - \frac{B}{2} \), where \( V \) is the number of valence electrons in the free atom, \( N \) is the number of non - bonding (lone pair) electrons, and \( B \) is the number of bonding electrons.

• For carbon (\( C \)):
• \( V = 4 \) (carbon has 4 valence electrons)
• \( N = 2 \) (2 non - bonding electrons)
• \( B = 6 \) (6 bonding electrons in \( C\equiv O \))
• \( FC = 4-2-\frac{6}{2}=4 - 2-3=-1 \)
• For oxygen (\( O \)):
• \( V = 6 \) (oxygen has 6 valence electrons)
• \( N = 2 \) (2 non - bonding electrons)
• \( B = 6 \) (6 bonding electrons in \( C\equiv O \))
• \( FC = 6 - 2-\frac{6}{2}=6-2 - 3=+1 \)
• For nitrogen (\( N \)):
• \( V = 5 \) (nitrogen has 5 valence electrons)
• \( N = 6 \) (6 non - bonding electrons)
• \( B = 2 \) (2 bonding electrons in \( O - N \))
• \( FC = 5-6-\frac{2}{2}=5 - 6-1=-2 \)

Answer:

atom	formal charge
\( O \)	\(+1\)
\( N \)	\(-2\)