Is CO2 polar or nonpolar? - Polarity of CO2

Global warming is on the rise all over the world and Carbon Dioxide (CO₂) is the main greenhouse gas contributing to it. CO₂ is a colorless gas with a sharp, acidic odor. It is released from the burning of fossil fuels in cars and in the industrial sector.

Considering the relevance and popularity of CO₂, it is very important to study its chemical properties such as its polarity. So, is CO₂ polar or nonpolar? Let’s find out through this article.

Is CO₂ polar or nonpolar? 

Carbon dioxide (CO₂) is a non-polar molecule. The non-polarity of CO₂ is accredited to its linear, symmetrical shape. A CO₂ molecule is composed of two different types of atoms i.e., a carbon atom and two atoms of oxygen.

The difference in electronegativities between the two atoms makes each C=O bond polar but the linear shape of the molecule cancels bond polarities in opposite directions. Thus, CO₂ is an overall non-polar molecule with a zero net dipole moment.

Name of molecule	Carbon dioxide (CO2)
Bond type	Polar covalent
Molecular geometry	Linear
Polar or Non-polar?	Overall Nonpolar molecule
Dipole moment	Zero
Bond angle	180º

What is polarity?

Polarity is a concept largely related to covalently bonded atoms in a molecule. If the electron cloud density is not equally shared between different atoms in a molecule then that molecule is polar.

If the electron cloud density is equally shared between the atoms of a molecule in that case the molecule will be overall non-polar such as CO₂.

There are three factors that control the polarity of CO₂ namely:

• Electronegativity
• Dipole moment
• Molecular geometry or shape

Below is a detailed discussion on each of these three factors which will help you in understanding the non-polar nature of CO₂ better.

Three Factors that make CO₂ nonpolar 

Electronegativity 

The attractive force between atoms created by sharing an electron pair is called a covalent bond.

The ability of an atom to strongly attract the shared electron pair towards itself from a bond is called its electronegativity.

Electronegativity disturbs the shared electron cloud in such a manner that one atom gains a partial positive charge while the other acquires a partial negative charge. Thus, the bond is known as a polar covalent bond.

If two atoms involved in a covalent bond have an electronegativity difference between 0.5 to 1.6 units then the bond will be polar.

A CO₂ molecule consists of two C=O double covalent bonds. There is carbon at the center while two oxygen atoms are bonded to it, one on each side.

Carbon (C) belongs to group IV-A (or group 14) of the Periodic Table. The electronic configuration of carbon is 1s²2s²2p², so it has 4 valence electrons. On the other hand, the electronic configuration of oxygen is 1s²2s²2p⁴, thus it has six valence electrons available for bonding.

Atom	Electronic configuration	Valence electrons
Carbon (6C)	1s2 2s2 2p2	4
Oxygen (8O)	1s2 2s2 2p4	6

Oxygen is a highly electronegative element. It is more electronegative (E.N= 3.44) than carbon (E.N = 2.55). So, it strongly attracts the shared electron cloud from each C=O bond.

The electronegativity difference is greater than 0.5 i.e., 3.44-2.55 = 0.89. Thus, each C=O bond in the CO₂ molecule is polar.

The central carbon attains a partial positive charge (C^δ+) while the oxygen atoms on both ends obtain a partial negative charge (O^δ-).

This phenomenon is called the bond polarity of C=O in a CO₂ molecule.

Dipole moment

The dipole moment is a vector quantity that represents the polarity of a bond and/or a molecule.

It has a symbol µ and is defined as the product of electrical charge (Q) and charge separation i.e., bond length (r). Debye (D) is the symbol used for dipole moment.

⇒ µ= Q.r

Simply put, the dipole moment represents the direction of polarity in a polar bond or molecule.

The dipole moment arrow points from the partial positive to the partial negative center of the bond.

Each C=O bond in the CO₂ molecule is polar so it has a dipole moment value approximately equal to the difference in electronegativity between the two atoms i.e., 0.89 D. It points from C^δ+ to O^δ-.

Molecular geometry

As we have already discussed that each C=O bond in CO₂ is individually polar with a specific dipole moment value. Then why is the overall CO₂ molecule non-polar?

This is due to the third very important factor i.e., the symmetrical geometry and shape of the molecule. 

According to the Valence Shell Electron Pair Repulsion (VSEPR) theory of chemical bonding, CO₂ is an AB2-type molecule. The central C atom (A) is bonded to two O atoms (B).

There are a total of 16 valence electrons in the CO₂ molecule. All the valence electrons of the carbon atom are involved in bond formation so there is no lone pair on Carbon.

However, there are 2 lone pairs on each Oxygen atom. All three atoms achieve a complete octet electronic configuration.

CO₂ has a linear shape with a mutual bond angle of 180°. The symmetrical arrangement of atoms cancels the dipole moments of C=O bonds in opposite directions. The net dipole moment of CO₂ is thus zero and CO₂ is a non-polar molecule overall.

Difference between polar and non-polar molecules

Polar molecule	Non-polar molecule
Atoms having a difference in electronegativity	Atoms may have the same or different electronegativity values
Unequal charge distribution overall	Equal charge distribution overall
Net dipole moment greater than 0	Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3) and sulfur dioxide (SO2), etc.,	Examples include oxygen (O2), nitrogen (N2), methane (CH4), and carbon dioxide (CO2).

Also check –

• CO2 lewis structure, molecular geometry, bond angle
• How to tell if a molecule is polar or nonpolar?
• Is SF4 polar or nonpolar?
• Is NH3 polar or nonpolar?
• Is SO2 polar or nonpolar?
• Is SO3 polar or nonpolar?
• Is H2O polar or nonpolar?
• Is H2S polar or nonpolar?
• Is HCN polar or nonpolar?
• Is CCl4 polar or nonpolar?
• Is XeF4 polar or nonpolar?
• Is CH2O polar or nonpolar?
• Is CHCl3 polar or nonpolar?
• Is BrF5 polar or nonpolar?
• Is SF6 polar or nonpolar?
• Is BF3 polar or nonpolar?
• Is PCl5 polar or nonpolar?

FAQ

Why CO2 is a nonpolar molecule?

The bonds in CO2 are polar because of the electronegativity difference between oxygen and carbon. The shape of CO2 is symmetrical linear geometry. All the atoms lie in the same plane and form a mutual bond angle of 180° which cancels the dipole moments of C=O bonds in opposite directions. This lead to a net dipole moment in CO2 equal to zero, therefore, the overall CO2 molecule is nonpolar in nature although the bonds in it are polar.

How is the carbon-oxygen bond in CO2 polar but the molecule is nonpolar?

The carbon-oxygen (C=O) bond in CO2 is polar because of the electronegativity difference between the two atoms. Oxygen more strongly attracts the shared electron cloud from a C=O bond. So, O becomes Oδ- due to a slight excess of electrons while C becomes Cδ+ due to a slight deficiency of electrons. The molecule however is non-polar because CO2 has a symmetrical, linear arrangement of atoms such that the polarity of individual C=O bonds gets canceled in opposite directions.

CO2 is nonpolar while SO2 is polar. Why?

CO2 is made up of two polar C=O bonds. However, it has a symmetrical linear shape with a 180° bond angle, no lone pair on central C, and the polarity (dipole moments) of C=O bonds get canceled in opposite directions, so CO2 is an overall non-polar molecule. Contrarily, SO2 also has two polar S=O bonds but there is a lone pair present on the central S atom. Lone pair-bond pair repulsions lead to the bent / V-shape of SO2 with a 119° bond angle. This asymmetrical shape makes SO2 a non-polar molecule.

Why is CO2 nonpolar and H2O polar?

CO2 has a symmetrical linear shape. The bond polarities of C=O bonds get canceled in opposite directions, so CO2 is a non-polar molecule with a net dipole moment of 0. H2O on the other hand is a polar molecule because of its asymmetric bent structure. The difference in electronegativities between O and H atoms makes each O-H bond in H2O polar. There are two lone pairs on the central O atom. Lone pair-lone pair and lone pair-bond pair repulsions decrease the bond angle and make H2O a bent shape. The dipole moments do not get canceled, unlike CO2.

Which is more polar, CO2, NH3, or N2O?

CO2 is a non-polar molecule because of its linear symmetrical shape and geometry. N2O also has a linear shape but still, it is a slightly polar molecule in comparison to CO2. The oxygen and nitrogen atoms in N2O have a little electronegativity difference (0.5 units) because of which the electron cloud density stays non-uniformly distributed over the N2O molecule. As a result, N2O is considered a polar molecule with a net dipole moment > 0. NH3 is the most polar out of the three molecules. It has polar N-H bonds, arranged asymmetrically in a trigonal pyramidal shape. There is a lone pair on N that repels the N-H bond pairs. So NH3 is an overall polar molecule with a net dipole moment of 1.4 D. Do check the complete details about – NH3 molecular geometry or shape CO2 molecular geometry or shape

CO2 is nonpolar, H2O is polar, but CO2 diffuses in H2O. How is this possible? CO2 is a non-polar molecule overall, but it has polar ends present. It uses these polar Oδ- ends and the Cδ+ center to interact with polar water molecules. It does not however diffuse or dissolve extremely well in water rather two distinct phases remain. That means a lot of CO2 is required to interact with water in order to obtain a little carbonic acid (H2CO3). The acidic taste and the fizz produced when you open your fizzy drink can are actually because of this CO2.

Explain hybridization in CO2?

The central carbon in the CO2 molecule is sp hybridized. The electronic configuration of C is 1s22s22p2 which cannot sufficiently form bonds with oxygen atoms. So, one 2s electron of carbon shifts to a 2p orbital. The valence shell configuration becomes 2s12px12py12pz1. The 2s and 2px orbital combine to form 2 sp hybrid orbitals while the py and pz orbitals stay unhybridized. Conversely, O has an electronic configuration of 1s22s22p4. It also hybridizes by using its 2s and two of the three 2p orbitals to form three sp2 hybrid orbitals. The pz orbital in CO2 stays unhybridized. Two sp2 hybrid orbitals of oxygen each have a lone pair of electrons which appear as un-bonded pairs on each O atom in CO2. Oxygen uses the third sp2 hybrid orbital to form a sigma bond with C while the unhybridized pz orbital of O forms a pi bond with the p orbital of C. There are two sigma bonds and two pi bonds in CO2 which facilitates the symmetrical arrangement and linear geometry of the molecule further endorsing the non-polar nature of carbon dioxide.

Summary

• Carbon dioxide (CO₂) is a non-polar molecule.
• It is due to the symmetrical linear molecular shape and geometry of CO₂ that the dipole moments of C=O bonds get canceled in opposite directions, so the molecule is non-polar overall.
• There is an electronegativity difference of 0.89 units between a carbon and an oxygen atom.
• Each C=O bond is polar with a dipole moment of 0.89 D that points from the partially positively charged C^δ+ to the partially negatively charged O^δ-.
• The central carbon atom in CO₂ is sp hybridized while each oxygen on the sides is sp² hybridized.
• C=O bond length in CO₂ is 116.3 pm while the O=C=O bond angle is 180° which confirms the linear shape of the molecule