Lewis structure of CO32-

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The Lewis structure of CO₃^2- contains two single bonds and one double bond, with carbon in the center, and three oxygens on either side. The top oxygen atom and left oxygen atom has three lone pairs, the right oxygen atom has two lone pairs, and the carbon atom does not have any lone pair.

Plus, there is a negative (-1) charge on the top oxygen atom and left oxygen atom.

Steps

By using the following steps, you can easily draw the Lewis structure of CO₃^2-.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Complete octet on central atom
#5 Calculate formal charge and check stability

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… carbon is a group 14 element and oxygen is a group 16 element. Hence, carbon has four valence electrons and oxygen has six valence electrons.

Now CO₃^2- has one carbon atom and three oxygen atoms.

So the total number of valence electrons = valence electrons of carbon atom + (valence electrons of oxygen atom × 3)

And CO₃^2- has a negative (-2) charge, so we have to add two more electrons.

Therefore, the total number of valence electrons = 4 + 18 + 2 = 24

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for carbon and oxygen as follows:

Electronegativity value of carbon = 2.55
Electronegativity value of oxygen = 3.44

Obviously, carbon is less electronegative than oxygen. Hence, assume that carbon is the central atom.

So now, put carbon in the center and oxygens on either side. And draw the rough skeleton structure for the Lewis structure of CO₃^2- something like this:

Also read: How to draw Lewis structure of SO₄^2- (5 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since carbon is surrounded by three oxygens, use six electrons to show three chemical bonds as follows:

#3 Mark lone pairs

As calculated earlier, we have a total of 24 valence electrons. And in the above structure, we have already used six valence electrons. Hence, eighteen valence electrons are remaining.

Two valence electrons represent one lone pair. So eighteen valence electrons = nine lone pairs.

Note that both (carbon and oxygen) are the period 2 elements, so they can not keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are oxygens, so each oxygen will get three lone pairs. And the central atom (carbon) will not get any lone pair, because all nine lone pairs are used.

So the Lewis structure of CO₃^2- looks something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (carbon) doesn’t form an octet.

So in the next step, we have to complete the octet on the central atom.

Also read: How to draw Lewis structure of SiS₂ (5 steps)

#4 Complete octet on central atom

Remember that carbon is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Now carbon already has six valence electrons. Hence, carbon needs two more valence electrons to complete its octet.

So convert one lone pair from one oxygen atom to make a new bond with the carbon atom. And then, the Lewis structure of CO₃^2- looks something like this:

In the above structure, you can see that the octet is completed on the central atom (carbon), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of PBr₅ (4 steps)

#5 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

• For carbon atom

Valence electrons = 4
Nonbonding electrons = 0
Bonding electrons = 8

Formal charge = 4 – 0 – ½ (8) = 0

• For top oxygen and left oxygen atom

Valence electrons = 6
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 6 – 6 – ½ (2) = -1

• For right oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of CO₃^2- looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of CO₃^2-.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

Now CO₃^2- is an ion having a negative (-2) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of CO₃^2- looks something like this:

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Related

• Lewis structure of SO₄^2-
• Lewis structure of SiS₂
• Lewis structure of PBr₅
• Lewis structure of OCS
• Lewis structure of H₃O⁺

External links

• Lewis Structure for CO32- | Carbonate ion – Chemistry School
• CO32- Lewis Structure in 6 Steps (With Images) – Pediabay
• What is the Lewis structure of CO32-? – Quora
• CO32- lewis structure, molecular geometry, and bond angle – Topblogtenz
• CO32- Lewis Structure, Molecular Geometry, Hybridization, and MO Diagram – Techiescientist
• Lewis Dot of Carbonate CO32- – Kent’s Chemistry
• Chemical Bonding: CO32- Lewis Structure – The Geoexchange
• CO32- Lewis Structure, Geometry – Kemicalinfo
• Draw a Lewis structure for CO32 – Homework.Study.com
• Lewis structure of carbonate ion CO32 – Chemistry Online
• For CO32, carbonate ion, draw the Lewis structure (by counting valence electrons of each atom) – Course Hero
• How many resonance structures are there for CO₃^2-? – Socratic
• How many equivalent Lewis structures are there for CO32-? – Answers
• Draw the Lewis structure for CO32- including any valid resonance structures – Brainly
• Carbonate (CO32-) Formal Charge – Chemistry Learner
• The Lewis structure for the carbonate ion CO32- shows ____ double bond(s), ____ single bond(s), and ____ lone pair(s) on the central atom – Numerade