Question

How do you calculate the formal charge of all atoms in ${{\mathrm{NO}}_3}^{-}$ ?

Answer 1

Step 1: Formula for formal charge:-

Formal charges are represented as the actual charges on any atom within a molecule, for which we can use the formula as;

$\mathrm{F}.\mathrm{C}=\mathrm{V}-\mathrm{N}-\frac{\mathrm{B}}{2}$

(Where V = number of valence electrons, N = number of nonbonded electrons, B = Number of bonded electrons )

Step 2: Structure of ${{\mathrm{NO}}_3}^{-}$, for understanding bonding within it:-

For ${{\mathrm{NO}}_3}^{-}$, the formal charges on each atom can be depicted by analyzing its structure given by;

Step 3: Calculation of formal charge for each atom:-

From the structure, we can see Nitrogen has 5 valence electrons and 8 bonding electrons, hence its formal charge is counted as:

$5-\frac{8}{2}=+1$

Similarly, for the first Oxygen, 6 nonbonding electrons and 2 bonding electrons with 6 valence electrons are there, hence the Formal charge on

${\mathrm{O}}_1$: $6-6-\frac{2}{2}$$=-1$

For the second Oxygen atom, the Formal count would be the same i.e ${\mathrm{O}}_2$$=-1$

For the third Oxygen, it has 4 nonbonding electrons and 4 bonding electrons with 6 valence electrons hence the Formal charge on

${\mathrm{O}}_3$:$6-4-\frac{4}{2}=0$

Hence, the formal charges of all atoms For ${{\mathrm{NO}}_3}^{-}$ has been calculated as; +1 for Nitrogen, -1 for first and second Oxygen, and 0 for third Oxygen.