CO2 Lewis Structure, Molecular Geometry, Molar Mass & Hybridization

Lewis Structures, Introduction, Formal Charge, Molecular Geometry, Resonance, Polar or Nonpolar
Lewis Structures, Introduction, Formal Charge, Molecular Geometry, Resonance, Polar or Nonpolar

In this article, we are going to learn about carbon dioxide (CO2) Lewis dot structure, molecular geometry, hybridization, molar mass, and many other aspects of CO2 in full details.

We will guide you to clear each doubt and misunderstanding for what you are here. So, without wasting your time, let’s start…

Carbon dioxide which chemical formula is CO2 is a colorless gas found on the earth’s atmosphere as a trace gas. The CO2 molecule is a triatomic molecule in which carbon is covalently double bonded with oxygen on both sides where bond length is around 116.3 pm.

Carbon dioxide is widely used in the food industry, oil industry, chemical industry, biological industry, and many more. Most commonly it is used as a fire extinguisher in daily life. It has a direct and very close relationship with human as we emission CO2 after intake of O2.

Contents

  • CO2 Lewis Structure
  • CO2 Molecular Geometry and Shape
  • CO2 Bond Angle
  • CO2 Hybridization
  • CO2 Molar Mass
  • CO2 Acid or Base
  • CO2 Polar or Nonpolar

CO2 Lewis Structure

CO2 has a total of 16 valence electrons (carbon has 4 and two oxygen have 12) which are structured as O=C=O. Both oxygen and carbon atoms need 8 electrons to complete octet in their outermost shells.

Here both oxygen atoms share two-two electrons with the carbon atom to form two double bonds (O=C) which can also represent by simply placing four dots for a double bond as shown in the above figure.

Steps to be followed for drawing CO2 Lewis structure

1. Find out the total number of valence electrons

CO2 is made up of two different atoms: Carbon (C) and Oxygen (O) so first, we should figure out the valence electrons of these two atoms separately.

Valence electrons of carbon atom = 4

Valence electron of oxygen atom = 6

Here in this molecule, we have one carbon atom and two oxygen atoms. Now,

Total number of valence electrons: 4 + 6*2 = 16.

2. Determine the total number of valence electrons pairs

As we know the total number of valence electrons are equal to the addition of sigma bonds, pi bonds, and lone pair present at the valence shells. But it can be simply calculated by just dividing the total number of valence electrons by two.

For CO2, total valence electrons are 16 (as calculated in step 1), so total electrons pairs are 16/2= 8.

3. Find out the central atom

Finding the central atom while drawing a Lewis structure is one of the trickiest parts but as described in how to draw a Lewis structure guide, there is a simple trick for selecting the central atom which is obviously saving extra time and energy.

The carbon atom is in the least number so simply it will be the central atom centralized by two oxygen atoms from either side.

4. Drawing a simple skeleton

As we have already known the central atom so we can easily draw a simple structure placing a carbon atom in the center surrounded by two oxygen from either side. The skeleton looks like shown in the above diagram,

5. Put the lone pairs of electrons on atoms

It is time to put lone pairs of electrons on atoms. For this, you must make sure every atom except the central atom must have 8 electrons to follow the octet rule (hydrogen is an exception because it follows duplet rules).

Place 6 electrons (three lone pairs of electrons) on each carbon atom and 4 electrons (two lone pairs of electrons) on the carbon atom.

We used all 16 valence electrons. Now check whether all atoms are completing octet or not on their outer shell, no they aren’t. Let’s check by sharing one lone pair of electrons but again fail to complete the octet. So, let’s share two pairs of electrons between both Carbon and Oxygen. Here we go each atom have now 8 electrons on its outermost shell which fulfills their octet.

6. Identifying formal charge on the atom

The formal charge on each atom can be calculated as,

Formal charge (F.C) = Valence electrons (V) – Lone pair of electrons (L) – Bond pair of electrons (B)/2.

From this, we get no charge on the molecule. Finally, this is our CO2 Lewis structure diagram.

CO2 Molecular Geometry & Shape

In a CO2 molecule, the carbon atom is in the center double bonded with two oxygen atoms by each side. Both oxygen atoms have two lone pairs of nonbonding electrons present and the central carbon atom has no lone pairs of nonbonding electrons present.

The presence of same atoms on either side of the central carbon atom nullifies the charge distribution because of the symmetrical structure. Thus, CO2 has a linear molecular geometry.

I) Electron Domain (ED) Geometry

From the above Lewis dot structure, CO2 has only two regions of electron density around the central carbon atom because no lone pair of electrons presence of carbon atom.

Both oxygen atoms have two lone pair of electrons presence but due to the symmetrical structure, the effects of lone pairs are canceled which results in a linear geometry of CO2, not bent or angular.

II) VSEPR Shape

According to VSEPR theory, there is a total of 16 valence electrons in which C contributes 4 electrons and two O contribute 12 electrons.

From the Lewis structure of Carbon, we know that there are not any lone pair of electrons presence on carbon.

Also, four pairs of electrons participate in the two C=O formations that show there are a total of 4 pairs of electrons pairs present which forms two sigma bond.

But the effects of lone pairs of oxygen atoms are nullified due to the symmetrical structure, the CO2 molecule acquires linear molecular geometry and has a linear shape.

Per the VSEPR model, a simple triatomic Molecule like CO2 has a structure AX2 and no lone pair of electrons, we consider two chemical bonds to extend in opposite directions, producing a linear molecule.

CO2 Bond Angle

As the molecular geometry of the CO2 is linear and arrangement like O=C=O which causes the bong angle of CO2 becomes 180°. The planer shaped geometry also known as linear geometry’s molecules have always 180° bond angle.

CO2 Hybridization

CO2 has an sp hybridization type. The central carbon atom has two regions that are responsible for identifying hybridization. Here C has only two sigma bonds and no lone pairs of electrons. And due to these two regions around the central carbon atom, CO2 has sp hybridization.

According to the VSEPR theory, we can identify the hybridization of any atoms based on their steric number (SN) which is given as,

Steric Number (SN) = total number of lone pairs + number of atoms directly attached with the atom.

If the steric number is 2 atoms have sp hybridization, if SN is 3 it will be sp2 hybridization, and so on…

In the case of CO2, The carbon atom has no lone pair of electrons but the C atom is attached to two other O atoms. So, the steric number of C atom will be 2 and it has sp hybridization.

But oxygen atoms have sp2 hybridization because oxygen atom’s steric number is 3 due to two lone pair and attached atom which is carbon.

Now as per hybridization rules, the hybridization of the whole molecule must be decided upon the central atom and carbon is the central atom in CO2 molecule so that CO2 molecule has sp hybridization.

We can also find out hybridization of the molecule directly with the help of a simple formula. The calculation is showing below,

Hybridization = ½ [V.E + M – C + A]

Where,

V.E = Total no. of valence electrons presence central on the molecule

M = Total number of monoatomic atoms bonded to the central atom

C = Cation charge (positive charge)

A= Anion charge (negative charge)

Now, on the above hybridization formula, we have to put corresponding values to achieve CO2 hybridization.

Hybridization of CO2 = ½ [ 2+2+0] = 2

= sp

CO2 Molar Mass

Molar mass (M) of any molecule is defined as the total sum of the mass of each atom in the molecules in grams per mole. Molar mass is also known as molecular weight. Basically, it is a physical property that is the division of the given substance to the amount of substance. Its unit is grams per mole.

Molar mass can be calculated by using this simple formula,

Molar mass = Grams/mole

Calculate the molar mass of CO2:

To calculate the molar mass of CO2, first, we have to find out the molar mass of Carbon and Oxygen which are 12.011g/mol and 16 g/mol respectively.

In CO2, there are one carbon atom and two oxygen atoms. So, the molar mass of CO2 is equal to (1*12.011 g/mol + 2*16 g/mol) = 44.011 g/mol.

CO2 Acid or Base

CO2 (Carbon dioxide) is considered as a Lewis acid due to the resonance structure of CO2 which means it can accept a lone pair of electrons from Lewis bases which are electron donors.

According to the Bronsted-Lowry acid-base definition, molecules that accept electrons are acids and those which are donated electrons are bases. So, it is considered a Bronsted acid.

When CO2 is dissolved in water (H2O), the reaction takes place between Lewis donor (H2O) and CO2 which gives carbonic acid (H2CO3). But it is in the form of H+ and HCO3- in equilibrium condition because H2CO3 is a very weak acid capable of dissociating H+ ions in a reversible form. This is also a very well-known example Le-Chatelier principle. You can see the whole reaction mechanism in the below example no. 1.

There is also another theory that explains why CO2 is acid on bond formation. The central carbon atom is attached which double bonds with oxygen. Thus, pi electrons get shifted to terminal electronegative atom causes it renders a vacant orbital with central atom because a Lewis base (OH-) can easily donate lone pair of electrons to the central atom (C).

SO2 and CO2 are the best examples of these types of Lewis acids.

Here are some of the example reactions which show CO2 (Carbon dioxide) is an acid:

1. CO2 (aq.) + H2O (l.) ⇌ H2CO3 (carbonic acid) ⇌ H+ (free hydrogen ion) + H2CO3- (bicarbonate ion)

CO2 Polar or Nonpolar

Carbon dioxide (CO2) is a nonpolar molecule despite two C and O bonds are polar. This is because the molecular geometry of CO2 is linear and is arranged symmetrically so that the dipole charges on either side get cancel which results in a net dipole moment is zero.

Because of net dipole charge of CO2 molecule is zero, there are not any polarity effects on molecule despite the presence of two Carbon and oxygen polar bonds.

You can read more about this specific topic separately in brief on our other article which named Polarity of CO2.

Conclusion

Carbon dioxide (CO2) has a total of 16 valence electrons which present on the outer shell of atoms i.e. 4 carbon atoms and 12 of two oxygen atoms. From this we can easily draw the Lewis dot diagram of CO2 by adjusting two double bonds between carbon and oxygen (O=C=O).

The molecular geometry of CO2 is linear with a bond angle of 180° because the dipole charges are canceled by each other as molecule is symmetrically arranged. Although both C=O bonds are polar but the entire molecule is nonpolar in nature.

When CO2 is dissolves in water, it produces H+ ions in the form of carbonic acid so that its shows acidic behavior and considered as an acid.

Point To Be Remember

These are some of the key points of the whole article which are very important and covered all the essential information about the CO2 molecule. So, if you want, you can note this for quick remembrance.

  1. CO2 has a total of 16 valence electrons (carbon has 4 and oxygen 6 valence electrons).
  2. CO2 has a linear molecular geometry with a bond angle of 180° on a plan.
  3. Molar mass of CO2 is 44.01 g/mol which is also known as molecular weight.
  4. Carbon dioxide has an sp hybridization type because the steric number of central carbon is 2.
  5. Carbon dioxide is a polar molecule but both C=O bonds are polar bonds.
  6. CO2 is considered as an acid because on dilution which water it produces free hydrogen ions.

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