Lewis Structure of CO3 2- (With 6 Simple Steps to Draw!)

I’m super excited to teach you the lewis structure of CO3 2- in just 6 simple steps.

Infact, I’ve also given the step-by-step images for drawing the lewis dot structure of CO3 2- ion.

So, if you are ready to go with these 6 simple steps, then let’s dive right into it!

Lewis structure of CO3 2- contains one double bond and two single bonds between the Carbon (C) atom and Oxygen (O) atom. The Carbon atom (C) is at the center and it is surrounded by 3 Oxygen atoms (O). Both the single bonded Oxygen atoms (O) have -1 formal charge.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of CO3 2-).

6 Steps to Draw the Lewis Structure of CO3 2-

Step #1: Calculate the total number of valence electrons

Here, the given ion is CO3 2- ion. In order to draw the lewis structure of CO3 2- ion, first of all you have to find the total number of valence electrons present in the CO3 2- ion.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in CO3 2-

• For Carbon:

Carbon is a group 14 element on the periodic table. ^[1]

Hence, the valence electrons present in carbon is 4 (see below image).

• For Oxygen:

Oxygen is a group 16 element on the periodic table. ^[2]

Hence, the valence electron present in oxygen is 6 (see below image).

Hence in a CO3 2- ion, 

Valence electrons given by Carbon (C) atom = 4
Valence electrons given by each Oxygen (O) atom = 6
Electron due to -2 charge, 2 more electrons are added
So, total number of Valence electrons in CO3 2- ion = 4 + 6(3) + 2 = 24

Step #2: Select the center atom

While selecting the atom, always put the least electronegative atom at the center. 

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[3]

Here in the CO3 2- ion, if we compare the carbon atom (C) and oxygen atom (O), then the carbon is less electronegative than oxygen.

So, carbon should be placed in the center and the remaining 3 oxygen atoms will surround it.

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of CO3 molecule, put the two electrons (i.e electron pair) between each carbon atom and oxygen atom to represent a chemical bond between them.

These pairs of electrons present between the Carbon (C) and Oxygen (O) atoms form a chemical bond, which bonds the carbon and oxygen atoms with each other in a CO3 molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of CO3, the outer atoms are chlorine atoms.

So now, you have to complete the octet on these oxygen atoms (because oxygen requires 8 electrons to have a complete outer shell).

Now, you can see in the above image that all the oxygen atoms form an octet.

Also, all the 24 valence electrons of CO3^2- ion (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch.

Let’s move to the next step.

Step #5: Check whether the central atom has octet or not. If it does not have an octet, then move the electron pair from the outer atom to form a double bond or triple bond

In this step, we have to check whether the central atom (i.e carbon) has an octet or not. 

In simple words, we have to check whether the central Carbon (C) atom has 8 electrons or not.

As you can see from the above image, the central atom (i.e carbon) has only 6 electrons. So it does not fulfill the octet rule.

Now, in order to fulfill the octet of a carbon atom, we have to move the electron pair from the outer atom (i.e oxygen atom) to form a double bond.

Now you can see from the above image that the central atom (i.e carbon), is having 8 electrons. So it fulfills the octet rule.

Step #6: Final step – Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on the carbon atom (C) as well as each oxygen atom (O).

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

• For Carbon:
  Valence electrons = 4 (as it is in group 14)
  Nonbonding electrons = 0
  Bonding electrons = 8
• For single bonded Oxygen:
  Valence electron = 6 (as it is in group 16)
  Nonbonding electrons = 6
  Bonding electrons = 2
• For double bonded Oxygen:
  Valence electron = 6 (as it is in group 16)
  Nonbonding electrons = 4
  Bonding electrons = 4

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
C	=	4	–	0	–	8/2	=	0
Single bonded O	=	6	–	6	–	2/2	=	-1
Double bonded O	=	6	–	4	–	4/2	=	0

Let’s keep these charges on the atoms in the above lewis structure.

As you can see in the above sketch, there are two -ve charges on the oxygen atom, which indicates the 2- formal charge on the CO3 molecule.

Hence, the above lewis structure of CO3^2- ion is the stable lewis structure.

Each electron pair (:) in the lewis dot structure of CO3 2- ion represents the single bond ( | ). So the above lewis dot structure of CO3 2- ion can also be represented as shown below.

Related lewis structures for your practice:
Lewis Structure of NF2-
Lewis Structure of SO4 2-
Lewis Structure of ClO2
Lewis Structure of Br2
Lewis Structure of BeCl2 

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