Is O3 a polar or nonpolar substance?

In modern chemistry textbooks, O3, often known as ozone, is a well-known chemical molecule. Ozone, also known as trioxygen, is an inorganic chemical found in the Earth’s atmosphere that protects us from the Sun’s harmful ultraviolet rays. The topic of whether O3 is polar or non-polar is a well-known one.

In this essay, I’ll go through the solution to this question in great detail, as well as the chemical structure of the O3 molecule.

Is O3 polar or non-polar, then? Because of its bent molecular geometry, O3 is a polar molecule. The electric dipole moments of the bonds in O3 do not counterbalance, resulting in a net dipole moment. O3 (Ozone) is polar in nature as a result of this.

Let’s take a closer look at this.

O3 Molecular Structure

Let’s take a look at O3’s Lewis structure first. Oxygen (O) has an atomic number of 8 and a valence shell with 6 electrons.

The centre oxygen atom shares four electrons with the other two oxygen atoms to produce one double bond and one single bond.

People sometimes believe that if the centre oxygen atom forms one double bond and one single bond with the other two oxygen atoms, there should be three unbonding electrons left on it. On the middle oxygen atom, however, there are only two unbonded electrons left.

It’s because the O3 has two resonant structures that alternate between double and single bond formation on both sides. In the diagram above, both of these structures are depicted.

As a result, the Middle Oxygen atom has only one lone pair of electrons. The lone pair also offers stronger repulsion to bond pairs on both sides, bending the O3 molecular shape. The angle formed between its bond pairs is 116 degrees.

The O3 molecule is twisted in shape due to the lone pair-bond pair repulsion, resulting in a net dipole that imparts polarity to the molecule.

Why is O2 a non-polar gas whereas O3 is polar?

Two oxygen atoms are linked together with a double bond in the O2 molecule. Each of these atoms has two lone pairs on it, but because this molecule only comprises two atoms, O2 is linear in shape.

Also, because the atoms are the same (Oxygen atom), the molecule has no net dipole moment. As a result, the O2 molecule seems to be non-polar.

However, O3 is unique in that it has three atoms and hence has a bent form. The polar character of the O3 molecule is imparted by the bent form, which results in a net electric dipole.

Due to uneven lone pairs on all oxygen atoms, the ozone molecule has no symmetry and is twisted in shape.

Lone pair-lone pair repulsion is commonly known to be larger than bond pair-bond pair and lone pair-lone pair repulsion. As a result, the oxygen atoms in Ozone experience lone pair-lone pair repulsion, resulting in a bent form.

Because it includes more lone pairs than ordinary oxygen atoms, the outer oxygen atom coupled to the core atom has a partial negative charge. While the Oxygen atom in the centre has a partial positive charge.

Factors that influence a molecule’s polarity

Moment of dipole

The net dipole moment of a polar molecule is always positive. The dipole moment of ozone, for example, is 0.53 D. The SI unit of dipole moment is the Debye, which is symbolised by the letter ‘D.’

A nonpolar molecule’s net dipole moment is equal to 0 D. The polarity of a molecule is proportional to its net dipole moment value.

Electronegativity

If the electronegativities of both atoms in a molecule differ, then the link between them is polar. The greater the difference between atoms’ electronegativities, the greater the total polarity.

Both oxygen atoms have the same electronegativity in the structure of an oxygen molecule. As a result, O2 is nonpolar.

Symmetry

A molecule’s polarity and non-polarity can also be established simply by looking at its structural geometry. It is a polar molecule if the molecule has no symmetry, and it is a nonpolar molecule if the form is symmetrical.

Because of the difference in electronegativity, the C-O bond in the carbon dioxide gas molecule is polar. Because the CO2 molecule is symmetrical, both C-O bonds are at 180 degrees, cancelling out the polarity. As a result, CO2 is nonpolar.

We can determine if a molecule is polar or nonpolar by looking at these factors.

Ozone’s Characteristics

The ozone layer protects the planet from the sun’s UV rays. A layer forms around the spectrum of the atmosphere, which strongly absorbs UV radiation between 220-290 nm.

These UV rays can harm aquatic life and plants on the earth’s surface, as well as humans, if this layer is not there. The Ozone layer, on the other hand, is depleting as global warming accelerates.

Ozone has a higher density than ambient air. It has a vapour density of approximately 24.

When ozone is liquidated, it turns into a dark blue liquid.

Pure ozone exists in a gaseous state that is blue in colour and has a strong stench. When it solidifies, it forms violet-black crystals.

Ozone has a boiling point of roughly -112 degrees Celsius.

At atmospheric pressure, ozone is soluble in water. With an oxidation potential of 2.07 V, ozone is a good oxidant. It’s also utilised in water treatment because it’s a strong oxidant.

Because ozone is electrophilic, it reacts with other elements very selectively.

In water, ozone is less stable than in air. In water, Ozone has a half-life of around 20 minutes, but in air, it has a half-life of about 12 hours.

Because of its oxidising characteristic, it is utilised in water treatment to sterilise drinking water.

It’s also used for bleaching in the textile industry.

So, I hope you now know why ozone is polar and what its features are.

Read more: Is Co a Polar or Nonpolar Substance?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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