CO Lewis Structure, Molecular Geometry, Hybridization, And MOT Diagram


The Lewis structure merely takes into account the electrons present in the valence shell, neglecting the inner shell’s electrons. Carbon monoxide is made of two elements: carbon and oxygen.

Carbon belongs to group IVA element with four electrons in its outermost shell, while oxygen is in group VIA of the modern periodic table with six electrons in its outermost shell.


If you are among those who know nothing about the carbon monoxide Lewis structure or its geometry, this article will give you the information you need. Here, we discuss some interesting facts about carbon monoxide, Lewis structure, molecular geometry, molecular orbital diagram, uses, and much more.

Facts About Carbon Monoxide (CO) 

Carbon monoxide is a colorless and odorless gas. It is a byproduct of combustion from burning fuel. When carbon monoxide mixes with other gases in the air, humans cannot smell it. As little as 200 ppm (parts per million) of CO can build up in an enclosed space and result in serious illness or death.

Molecular name Carbon monoxide
Formula CO
Valence shell electrons 10
CO hybridization Sp
Molecular geometry Linear
Dipole moment 0.122D
Bond angle 180⁰
Formal charge Approximately zero
CO is polar or non-polar. Polar molecule

The Lewis Structure of Carbon Monoxide (CO) in 6 Easy Steps

The Lewis structure merely takes into account the electrons present in the valence shell, neglecting the inner shell’s electrons. A dot represents a lone pair of electrons in a Lewis structure, whereas a straight line indicates a bonded pair of electrons.

Step # 1

To Determine the Total Number of Valence Electrons

Carbon monoxide is made of two elements: carbon and oxygen. Carbon belongs to group IVA element with four electrons in its outermost shell, while oxygen is in group VIA of the modern periodic table with six electrons in its outermost shell.

To calculate the total outermost electrons of a particular element, multiply the number of atoms present in that element by its valence shell electrons.

Now let us calculate the valence shell electrons.

  • For Carbon

As carbon is an IVA element of the periodic table,

Therefore, the valence electrons in the outermost shell of carbon are four.

Mathematical representation

Valence electron (4)* no. of atom (1) = 4

Carbon Monoxide (CO)

For Oxygen

As oxygen is a VIA element of the modern periodic table,

Therefore, oxygen has six valence electrons.

Mathematical representation 

Valence electron (6) * no. of atoms (1) =6

Carbon monoxide CO

Hence, the total number of valence electrons present in the CO molecule = 4+6 = 10.

Step # 2

Calculate the Valence Electron Pair of the CO Molecule

The total electron pair of a molecule is the sum of sigma, pi, and the lone pair available in the valence shell of the molecule.

Mathematical representation

Total electron pair = sigma bond + pi bond + lone pair of valence electrons

To get the total electron pair, divide the number of valence electrons by two (2).

However, the total electron pair of carbon monoxide (CO) will be 10/2 = 5.

Step # 3

Identify the Central Atom

Being the central atom in a molecule comes with its own set of requirements. The capacity of an atom to have a large valence is essential for it to be central. More importantly, while determining which atom should be the center atom, the number of atoms as well as their electronegativity must be considered.

There is no need to worry about selecting the center atom in carbon monoxide because there are only two atoms.

Carbon Monoxide (CO)

Step # 4

Mark Lone Pair on Each Atom 

After finding the central atom and drawing the C-O molecule, we may begin to mark lone pairs on atoms.

It’s important to remember that there are a total of five lone pairs. Out of five lone pairs, one is already marked as C-O. Therefore, we have only four electron pairs to mark as lone pairs on the C-O bond.

Mark three lone pairs on the oxygen atom because there is no center atom. The oxygen atom will accept three lone pairs. One leftover lone pair is marked on the carbon atom.

Carbon Monoxide (CO)

Step # 5

Complete the Octet of Each C and O

To gain a stable Lewis structure, the atoms of the molecule must fulfill their octet.

In the above structure, an octet of carbon is not completed. Therefore, convert the lone pair of oxygen into a bond pair as below.

Carbon monoxide (CO)

Now, an octet of carbon is still unhappy (not complete) and we need to convert one of the lone pairs of oxygen into a bond. As a result, a triple bond forms between carbon and oxygen, and both have a complete octet.

carbon monoxide CO

Step # 6

Calculate the Formal Charge on Each Atom to Check the Stability

Let’s look at how the formal charge is calculated and what it signifies.

The following is the equation for calculating an atom’s formal charge:

FC (formal charge) = V (No. of valence electrons) -N (No. of non-bonded electrons) – B (No. of bonded electrons) /2

Now let’s determine the formal charge of carbon monoxide (CO).

Formal charge on C= (4)-(2) – (6)/2 =-1

Formal charge on O = (6) – (2) – (6)/2 = +1

As we already know, the smaller the formal charge, the more stable a molecule’s Lewis structure is. The below structure is the best Lewis dot structure for the molecule since it contains near to zero formal charge in its atoms.

Carbon Monoxide (CO)

Why it’s Important to Know About Lewis Structures

Lewis structures are important in predicting the geometry, polarity, and reactivity of compounds (organic & inorganic). Knowing an atom’s Lewis structure helps you predict how it will bond and how many bonds it will make.

This information will ultimately help us to understand the structure of molecules as well as their chemical make-up. 

 Carbon Monoxide (CO) Molecular Geometry & Shape 

The three-dimensional (3D) arrangement of atoms linked together to form a molecule is called molecular geometry. The molecular geometry of any molecule is essential because it offers information on a variety of physical and chemical properties, such as polarity, phase of matter, reactivity, color, biological activities, magnetism, and so on.carbon Monoxide CO

It is a diatomic molecule with a triple bond between the atoms of carbon and oxygen and one lone pair of electrons on each atom. Because it only has two atoms, it has a linear molecular geometry. When carbon and oxygen combine, one sigma bond and two pi bonds are created.

VSEPR theory is also used to calculate the shape or geometry of the CO molecule. We could employ the AXN technique for the determination of CO geometry.

Determination of Carbon Monoxide (CO) Geometry by the AXN Method

  • In AXN, “A” shows the central atom.
  • “X” represents the atoms bonded to a central atom. Only one carbon atom is bound to the central oxygen atom in the CO molecule. Therefore, X = 1.
  • “N” donates the lone pair of electrons present on the central atom. There is only 1 lone pair on the central atom. So, N=1


  • AXN (for CO) = AX1N1 or (AX).

If a molecule has an AX1 N1 formula, it has linear geometry, according to VSEPR theory. Therefore, the AXN formula proves that CO has linear geometry.

The Bond Angle of Carbon Monoxide (CO) 

The bond angle is the angle formed by the central atom and the bounded atoms.  The number of bonded atoms determines the Bond angle.  A larger bond angle would be the result of less repulsion.

Since CO only has two atoms, its molecular geometry is linear. The bond angle of carbon monoxide will be 180 degrees.

The Polarity of Carbon Monoxide (CO) 

Carbon monoxide is Polar in nature. A polar molecule has uneven electronegativity among its constituent atoms. This causes an electric charge imbalance across the molecule, giving it a net dipole moment. A polar covalent bond is established if the electronegativity difference between the atoms is 0.5–2.

The following are the factors that determine the polarity of any molecule.


Electronegativity describes how strongly an atom attracts electrons in a chemical bonding. The electronegativity difference between two atoms determines the chemical bond.

  • If the electronegativity difference is more than 2.1, the bond will be ionic.
  • When the electronegativity difference is 0.5 to 2.1, the bond will be polar covalent.
  • If the electronegativity difference between two atoms is less than 0.5, the bond will be non–polar.

 The greater value of electronegativity makes the covalent bond polar. Electronegativity values for carbon and oxygen are (2.55), and (3.44) respectively. The differences in electronegativity between both atoms (2.55-3.44 =0.89) make the C-O bond polar.

Dipole Moment

A dipole moment is a measurement of electrical charge separation. The dipole moment is large for the bonded atom which has a more electronegativity difference. Carbon Monoxide (CO) is a polar molecule because of the electronegativity difference and has a net dipole moment of 0.122D.

Carbon Monoxide (CO)

Molecular geometry

The shape of any molecule is a vital factor in depicting the polarity of the molecule. Because CO only has two atoms, it has a linear molecular geometry.

Hence, we could say that carbon monoxide (CO) is polar in nature.

Hybridization of Carbon Monoxide (CO) 

The carbon monoxide molecule has an sp hybridization. Hybridization is a process when two atomic orbitals of the same atom that have slightly different energies combine, redistributing energy between them and creating new orbitals with the same energies and shape. The new orbitals produced by this process are hybrid orbitals.

Since carbon monoxide has a linear combination, its hybridization is sp. The electronic valence shell arrangement of the carbon and oxygen atoms is shown in the diagram below.

Carbon Monoxide (CO)

Head-on overlap occurs between the half-filled sp(z) hybrid orbitals of the carbon and oxygen atoms. This creates the first bond, the sigma bond, which is the strongest of all.

The half-filled 2px orbital of the carbon atom interacts and overlaps with the half-filled 2px orbital of the oxygen atom in a sideways manner.

This results in a weak pi bond. Additionally, a sideways overlap between the filled 2py orbital of the oxygen and the 2py orbital of the carbon results in the formation of another pi bond.

                            Carbon Monoxide (CO)

As a result, two weak pi bonds and one strong sigma bond are created. 

This results in the formation of one strong and two weak covalent bonds between the carbon and oxygen molecules of carbon monoxide.

The Molecular Orbital Diagram of Carbon Monoxide (CO) 

A diagram that illustrates how chemical bonding occurs within a molecule is called a molecular orbital diagram.

It defines how pi and sigma bonds have formed inside the common covalent link, as well as the intensity in terms of strength.

Carbon monoxide has 10 valence electrons, six from oxygen atoms (2s2, 2p4) and four from carbon atoms (2s2, sp2). Therefore, the molecular orbital configuration according to the molecular orbital diagram is as follows:

σ2s² σ*2s² πx² πy² σz² π*x⁰ πy⁰ σ*z⁰


Bond order = 1/2(8–2) = 3


Because oxygen is more electronegative than carbon, its orbitals are more stable and have lower energies than carbon’s, under the idea of electronegativity.

Carbon and oxygen atoms each have three filled bonding orbitals.

On the other hand, two orbitals are not bonded. One is on the side of carbon, while the other is on the side of oxygen.

The Properties of Carbon Monoxide (CO) 

  • Carbon monoxide is a colorless, odorless gas.
  • The molecular weight of carbon monoxide is 28 grams.
  • It has an amphoteric property, i.e., it can react as either a base or an acid depending on the other ingredient used in the reaction with carbon monoxide.
  • Carbon monoxide is a so-called “heavy atom,” which means that it tends to bind to other carbon atoms.
  • It’s easily soluble in chemicals like ethanol, chloroform, acetic acid, ammonium hydroxide, benzene, and ethyl acetate.
  • It has a slightly lower density than air.
  • Its molar mass is around 28.0 g/mol.
  • The melting point of carbon monoxide is -205.02 degrees Celsius (or 337.04 degrees Fahrenheit).
  • Its boiling point is 191.5 degrees Celsius (or 312.7 degrees Fahrenheit).

Effects of Carbon Monoxide (CO) 

Continuous exposure to excessive carbon monoxide can cause serious disease in people and animals because it binds with hemoglobin in the blood (which transports oxygen to different regions of the body), and cause even death.

Symptoms of carbon monoxide poisoning include

  • Memory problems
  • Hearing loss
  • Loss of vision
  • Vomiting
  • Brain damage
  • Heart irregularity
  • Breathing difficulties
  • Muscles weakness

Uses of Carbon Monoxide (CO) 

  • It is used in the production of detergents.
  • The purification process uses CO.
  • It is used as a reducing agent.
  • It can also be used in methanol production.
  • It’s used in infrared laser.
  • For the removal of rust from the surface of the metal, carbon monoxide is used.
  • It is used to produce hydrogen by water gas shift reaction.
  • It is used to produce phosgene.
  • It’s used in metallurgy.

Concluding Remarks

Carbon monoxide (CO) exhibits a triple bond formation in its Lewis structure, with two weak pi bonds and one strong sigma bond. Furthermore, the lone pair of electrons contribute to the linear shape of the carbon monoxide (CO) molecule.

It may interest you to know that study of molecular orbital theory, instead of hybridization, is more appropriate for understanding carbon monoxide.

Frequently Asked Questions

What is the molecular geometry of Carbon Monoxide?

Carbon monoxide is a diatomic molecule containing one lone pair of electrons on each atom and a triple bond connecting the C and O atoms. Because it only comprises two atoms, it forms a linear combination or molecular geometry. One sigma bond and two pi bonds are formed between carbon and oxygen.                      

What is the polarity of carbon monoxide?

Carbon monoxide is polar in nature due to the electronegativity differences between carbon (2.55) and oxygen (3.44) atoms. Due to the uneven charge distribution on the carbon and oxygen atoms, the CO bond has a net dipole moment (which is 0.122D) making CO a polar molecule.

What type of bond is Carbon Monoxide?

The carbon monoxide molecule is represented by a triple covalent bond between the oxygen and carbon atoms. One of the bonds is a coordinate covalent bond, a type of covalent bond where one of the atoms provides both of the shared pair of electrons.

A coordinate covalent bond is identical to every other covalent bond after it has been created. It is not as if the two typical bonds in the CO molecule are stronger or differ in any manner from the coordinate covalent bond.

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