Question

Assign formal charges to each atom in the O3 molecule shown here. Be sure to click the +  or - button before clicking on the molecule.

Answer 1

Concepts and reason

The concept used to solve this problem is the formal charge calculation of the oxygen atoms present in the ozone molecule.

Fundamentals

A charge that is assigned to an atom, which is present in the molecule, is represented as a formal charge. In two bonded atoms, a formal charge assumes that the electrons are equally shared between them. The formal charge is calculated using the following formula:

Formal charge \(=\mathrm{V}-\mathrm{N}-\frac{\mathrm{B}}{2}\)

Here, \(\mathrm{V}\) is the number of valence electrons, \(\mathrm{N}\) is the number of non-bonding electrons and \(\mathrm{B}\) is the number of bonding electrons.

 

The structure is as follows:

Calculate the formal charge for the circled oxygen in ozone molecule as follows:

Formal charge \(=\mathrm{V}-\mathrm{N}-\frac{\mathrm{B}}{2}\)

\(\begin{aligned}=& 6-6-\frac{2}{2} \\ &=-1 \end{aligned}\)

Explanation | Common mistakes | Hint for next step

The marked oxygen atom has 6 valence electrons. It contains 6 non-bonding electrons. The marked oxygen atom is bonded with one oxygen atom. Therefore, the bonding electron of oxygen is \(2 .\) Substitute the values in a formal charge formula to determine the formal charge of oxygen (marked).

 

The structure is as follows:

Calculate the formal charge for the circled oxygen in ozone molecule as follows:

Formal charge \(=\mathrm{V}-\mathrm{N}-\frac{\mathrm{B}}{2}\)

\(=6-2-\frac{6}{2}\)

\(=+1\)

Explanation | Common mistakes | Hint for next step

The oxygen atom in the middle has 6 valence electrons and has 2 non-bonding electrons. The central oxygen atom is bonded with 1 double bond and 1 single bond. So, there is a total of 3 bonds containing 6 electrons (bonding electrons). The formal charge of the middle oxygen atom can be determined by substituting the values in a formal charge formula.

 

The structure is as follows:

Calculate the formal charge for the circled oxygen in ozone molecule as follows:

Formal charge \(=\mathrm{V}-\mathrm{N}-\frac{\mathrm{B}}{2}\)

\(=6-4-\frac{4}{2}\)

\(=0\)

The formal charge of each oxygen atom in \(\mathrm{O}_{3}\) molecule are labeled as follows:

The oxygen atom present on the right side contains 6 valence electrons which have 2 non-bonded electrons. The marked oxygen is bonded with 1 double bond with a central oxygen atom. So, the number of bonding electrons is \(4 .\) The formal charge of the corner oxygen atom (right corner) can be determined by substituting the values in the formal charge formula.

The formal charge of each oxygen atom in \(\mathrm{O}_{3}\) molecule are labeled as follows: