Question

What are the formal charges in ${\mathrm{O}}_3$(ozone)?

Answer 1

Formal charge:

• The formal charge of an atom in a molecule is the charge which might exist on the atom if all bonding electrons were evenly shared.
• A formal charge value is equal to an atom's valence electrons deducting the number of electrons given to it.
• $\mathrm{F}.\mathrm{C}.=[\mathrm{Total}\mathrm{no}.\mathrm{of}\mathrm{valence}{\mathrm{e}}^{–}\mathrm{in}\mathrm{free}\mathrm{state}]–[\mathrm{total}\mathrm{no}.\mathrm{of}\mathrm{non}-\mathrm{bonding}\mathrm{pair}{\mathrm{e}}^{–}(\mathrm{lone}\mathrm{pair}\left)\right]–\frac{1}{2}[\mathrm{total}\mathrm{no}.\mathrm{of}\mathrm{bonding}{\mathrm{e}}^{–}]$

Structure of ozone:

• Ozone has a dipole moment of $0.53\mathrm{D}$ and thus a polar molecule.
• The molecule can be described as a resonance hybrid with significant contributing structures, one with a single bond on one side and the other with a double bond.
• Both sides have an overall bond order of $1.5$ in this arrangement.
• 

Formal charge in ${\mathrm{O}}_3$ ( Ozone):

• In an ${\mathrm{O}}_3$ molecule, the formal charge on the middle oxygen atom($2$) is $+1$.

$$\begin{gathered} \mathrm{F}.\mathrm{C}=6–2–\frac{1}{2}\left(6\right) \\ \mathrm{F}.\mathrm{C}=6–5 \\ \mathrm{F}.\mathrm{C}=1 \end{gathered}$$

• In an ${\mathrm{O}}_3$ molecule, the formal charge on the left oxygen atom($3$) is $-1$.

$$\begin{gathered} \mathrm{F}.\mathrm{C}=6–6–\frac{1}{2}\left(2\right) \\ \mathrm{F}.\mathrm{C}=6-7 \\ \mathrm{F}.\mathrm{C}=-1 \end{gathered}$$

• In an ${\mathrm{O}}_3$ molecule, the formal charge on the right oxygen atom($1$) is $0$.

$$\begin{gathered} \mathrm{F}.\mathrm{C}=6–4–\frac{1}{2}\left(4\right) \\ \mathrm{F}.\mathrm{C}=6–6 \\ \mathrm{F}.\mathrm{C}=0 \end{gathered}$$