How to calculate formal charges of Carbon dioxide (CO2) with lewis structure?

In covalently bonded molecules, formal charge is the charge assigned to an atom based on the assumption that the bonded electrons are equally shared between concerning atoms, regardless of their electronegativity.

The overall formal charge present on a molecule is a measure of its stability.

The fewer the formal charges present on the bonded atoms in a molecule (close to zero), the greater the stability of its Lewis structure.

Interestingly, Carbon dioxide (CO₂) in a crowded place makes humans feel lethargic, while plants use the same gas molecules in their food generation process called Photosynthesis.

In this article, we will calculate the formal charges present on the bonded atoms in CO₂ and also the overall charge present on the molecule. 

So, let us not provoke your curiosity further and immediately start reading!

Name of the molecule	Carbon Dioxide
Chemical formula	CO2
The formal charge on the central C-atom	0
The formal charges on double-bonded O-atoms	0
The overall formal charge on CO2	0

How to calculate the formal charges on CO₂ atoms?

The formal charges can be calculated using the formula given below:

The formal charge of an atom = [valence electrons of an atom – non-bonding electrons – ½ (bonding electrons)]

• The valence electrons (V.E) of an atom are the total number of electrons present in its valence shell. Valence electrons can be determined by locating the position of the elemental atom in the Periodic Table.
• Non-bonding electrons (N.E) are the number of lone pairs present on the atom. (1 lone pair means 2 nonbonding electrons).
• Bonding electrons (B.E) are the total electrons shared with the atom via covalent chemical bonds. (1 single bond means 2 bonding electrons).

Now let us use this formula to calculate the formal charges in the most preferred Lewis structure of carbon dioxide CO₂.

The most preferred Lewis representation of the CO₂ molecule is as shown below.

It consists of a total of 16 valence electrons. One Carbon (C) atom is present at the center, which is bonded to two atoms of oxygen (O) via a double covalent bond, one on either side.

No lone pair of electrons is present at the central C-atom while each of the two double-bonded O-atoms contains 2 lone pairs of electrons, respectively.

It is the best possible Lewis structure of CO₂ because the formal charges are minimized in it, and thus, it is the most stable.

Let’s find out how we can determine the formal charges present on each atom in the CO₂ Lewis structure.

For the central Carbon atom

• Valence electrons of Carbon = It is present in Group IV-A = 4 valence electrons
• Bonding electrons around Carbon = 2 double bonds = 2(4) = 8 electrons
• Non-bonding electrons on Carbon = 0 lone pair = 0 electrons
• Formal charge on the Carbon atom = 4 – 0 – 8/2 = 0

∴ The formal charge on the central Carbon (C) atom in CO₂ is 0.

 For double-bonded Oxygen atom

• Valence electrons of Oxygen = It is present in Group VI A = 6 valence electrons
• Bonding electrons around Oxygen = 1 double bond = 4 electrons
• Non-bonding electrons on Oxygen = 2 lone pairs = 2(2) = 4 electrons
• Formal charge on the Oxygen atom = 6 – 4 – 4/2 = 6 – 4 – 2 = 6 – 6 = 0

∴ The formal charge on each double-bonded oxygen (O) atom in CO₂ is also 0.

This calculation shows zero formal charges are present on the central C-atom and two double-bonded O-atoms, as shown below. 

As a result, there is no overall charge on the CO₂ Lewis structure, and thus it is a neutral molecule.

Also, check –

• How to draw CO₂ lewis structure?
• Formal charge calculator
• SO₃ formal charge
• ClO₃^– formal charge
• HCN formal charge
• SO₄^2- formal charge
• PO₄^3- formal charge
• SO₃^2- formal charge
• CN^– formal charge
• SO₂ formal charge
• O₃ formal charge
• SCN^– formal charge
• POCl₃ formal charge
• NH₃ formal charge
• CO formal charge
• H₂O formal charge
• NH₄⁺ formal charge
• H₃O⁺ formal charge
• OH^– formal charge
• HSO₄^– formal charge
• ClO^– formal charge
• BH₄^– formal charge
• N₃^– formal charge
• H₂SO₄ formal charge
• NCO^– formal charge
• NO₃^– formal charge
• NO₂^– formal charge
• CH₃ formal charge

FAQ

How can you calculate CO2 formal charges?

The formal charges present on the bonded atoms in CO2  can be calculated using the formula given below: V.E – N.E – B.E/2 Where – ⇒ V.E = valence electrons of an atom ⇒ N.E = non-bonding electrons, i.e., lone pairs ⇒ B.E = bonding electrons

In the most stable Lewis structure of CO2, what is the formal charge on C-atom?

The central carbon (C) atom carries zero formal charges in the most stable CO2 Lewis structure.

What is the formal charge on O-atoms in CO2?

Zero or no formal charge is present on both double-bonded (C=O) oxygen atoms in CO2.

Do both O-atoms carry the same formal charge in CO2?

Yes, each of the two double-bonded O-atoms carries 0 formal charges in the CO2 Lewis structure.

What is the overall formal charge on CO2?

The overall formal charge on CO2 is 0.

Summary

• The best possible Lewis structure of a molecule is the one in which the bonded atoms carry formal charges as close to zero as possible.
• The formal charge formula is [ V.E – N.E – B.E/2].
• In the most stable Lewis structure of CO_2, zero formal charges are present on the central C-atom.
• The double-bonded O-atoms also have zero formal charges in CO
• The overall formal charge of CO₂ is zero, and thus it is a neutral molecule.