Carbon tetrachloride (CCl4) lewis dot structure, molecular geometry or shape, electron geometry, hybridization, bond angle
CCl4 is the chemical formula for carbon tetrachloride, aka tetrachloromethane, a sweet-smelling, non-flammable, chemically stable, colorless liquid.
It is used as an inert solvent in organic synthesis, as a soil fumigant, a fire extinguisher and the list goes on and on for the uses and applications of CCl4.
In this article, you will learn everything about the Lewis dot structure of CCl4, its molecular geometry or shape, electron geometry, bond angles, formal charges, hybridization, polarity, etc.
So, if you are curious to know all that and much more about carbon tetrachloride (CCl4), then continue reading the article!
The Lewis dot structure of carbon tetrachloride (CCl4) comprises a carbon (C) atom at the center. It is surrounded by four chlorine (Cl) atoms at the sides, each via a single covalent bond. There is no lone pair on the central C-atom. However, each of the four terminal Cl-atoms carries 3 lone pairs of electrons in the CCl4 Lewis structure.
Drawing the Lewis dot structure of CCl4 is super easy. So, come along and draw it with us by following the simple steps given below.
Steps for drawing the Lewis dot structure of CCl4
1. Count the total valence electrons present in CCl4
The two distinct elements present in CCl4 are carbon and chlorine.
Carbon (C) is present in Group IV A (or 14) of the Periodic Table, having a total of 4 valence electrons in each atom.
In contrast, chlorine (Cl) is a halogen located in Group VII A (or 17), implying that it has 7 valence electrons in each atom.
Total number of valence electrons in carbon = 4
Total number of valence electrons in chlorine = 7
The CCl4 molecule comprises 1 C-atom and 4 Cl-atoms.
∴ Therefore, the total valence electrons available for drawing the Lewis dot structure of CCl4 = 1(4) + 4(7) = 32 valence electrons.
2. Find the least electronegative atom and place it at the center
By convention, the least electronegative atom out of all those available is chosen as the central atom while drawing the Lewis structure of a molecule.
The least electronegative atom can easily form covalent bonds with other atoms by sharing its electrons.
Carbon (E.N = 2.55) is undoubtedly less electronegative than chlorine (E.N = 3.16).
Therefore, the C-atom is placed as the central atom in the CCl4 Lewis structure while the four Cl-atoms are spread around it at the terminals, as shown below.
3. Connect the outer atoms with the central atom
In this step, the outer atoms, i.e., 4 Cl-atoms, are joined to the central C-atom using single straight lines.
A straight line represents a single covalent bond, i.e., a bond pair containing 2 electrons.
In the above structure, there are 4 single bonds, i.e., 4(2) = 8 valence electrons are already consumed out of the 32 initially available.
Now let’s see in the next steps where to place the remaining 24 valence electrons in the CCl4 Lewis dot structure.
4. Complete the octet of the outer atoms
A Cl-atom needs a total of 8 valence electrons in order to achieve a stable octet electronic configuration.
A C-Cl bond represents 2 valence electrons already present around each chlorine atom in the Lewis structure drawn so far.
Therefore, the remaining 6 valence electrons are placed as 3 lone pairs around each Cl-atom to complete its octet.
5. Complete the octet of the central atom
Total valence electrons used till step 4 = 4 single bonds + 4(electrons placed around each Cl-atom, shown as dots) = 4(2) + 4(6) = 32 valence electrons.
Total valence electrons – electrons used till step 4 = 32 – 32= 0 valence electrons.
As all the valence electrons initially available for drawing the CCl4 Lewis structure are already consumed so there is no lone pair on the central C-atom.
However, we need not worry because the central C-atom already has a complete octet as per 4 single bonds surrounding it.
Hence, the final step is to check the stability of the CCl4 Lewis structure by applying the formal charge concept.
6. Check the stability of Lewis’s structure using the formal charge concept
The less the formal charge on the atoms of a molecule, the better the stability of its Lewis structure.
The formal charges can be calculated using the formula given below.
Formal charge = [valence electrons- nonbonding electrons- ½ (bonding electrons)].
Now let us use this formula and the Lewis structure obtained in step 5 to determine the formal charges present on the CCl4-bonded atoms.
What are the electron and molecular geometry of CCl4?
The molecular geometry or shape of carbon tetrachloride (CCl4) is identical to its ideal electron pair geometry, i.e., tetrahedral. There is no lone pair of electrons on the central C-atom; thus, no distortion is witnessed in the shape and geometry of the molecule.
Molecular geometry of CCl4
The molecular geometry or shape of carbon tetrachloride (CCl4) w.r.t the central C-atom is tetrahedral.
To a carbon atom at the center, four chlorine atoms are attached like four corners of a tetrahedron, and there is no lone pair of electrons on the central C- atom.
Hence no lone pair-lone pair or lone pair-bond pair electronic repulsions exist in the molecule.
The bonded atoms arrange themselves around the central atom to form a tetrahedral shape, as shown below.
Electron geometry of CCl4
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, the ideal electron geometry of a molecule containing a total of 4 electron density regions around the central atom is tetrahedral.
In CCl4, the C-atom at the center is surrounded by 4 bond pairs, and it has no lone pair of electrons, making a total of 4 electron density regions. Hence, the ideal electron pair geometry of the CCl4 molecule is tetrahedral.
An easy trick to finding a molecule’s electron and molecular geometry is using the AXN method.
AXN is a simple formula representing the number of bonded atoms and lone pairs present on the central atom.
It is used to predict the shape and geometry of a molecule using the VSEPR concept.
AXN notation for CCl4
A in the AXN formula represents the central atom. In the CCl4 molecule, a carbon (C) atom is present at the center, so A = C.
X denotes the atoms bonded to the central atom. In CCl4, 4 Cl-atoms are directly bonded to the central C-atom. Hence X =4 for CCl4.
N stands for the lone pairs present on the central atom. As per the Lewis structure of CCl4, the central C-atom has no lone pair of electrons. Thus, N = 0 for CCl4.
As a result, the AXN generic formula for CCl4 is AX4N0or simply AX4.
Now, you may have a look at the VSEPR chart below.
The VSEPR chart confirms that a molecule with AX4 generic formula possesses an identical electron and molecular geometry or shape, i.e., tetrahedral, as we already noted down for the carbon tetrachloride (CCl4) molecule.
Hybridization of CCl4
The central C-atom is sp3 hybridized in CCl4.
The electronic configuration of carbon is 1s2 2s2 2p2.
During chemical bonding in CCl4, one of the two 2s electrons of carbon shifts to its empty 2p atomic orbital. As a result, the half-filled 2s and three 2p atomic orbitals of carbon hybridize to produce four sp3 hybrid orbitals.
Each sp3 hybrid orbital possesses a 25 % s-character and a 75 % p-character. All four sp3 hybrid orbitals of carbon are equivalent and contain a single unpaired electron only.
Therefore, carbon uses these sp3 hybrid orbitals to form the C-Cl sigma bonds, one on either side of the CCl4 molecule by sp3-p orbital overlap, as shown below.
Another shortcut to finding the hybridization present in a molecule is using its steric number against the table given below.
The steric number of the C-atom in CCl4 is 4, so it has sp3 hybridization.
Steric number
Hybridization
2
sp
3
sp2
4
sp3
5
sp3d
6
sp3d2
The bond angles of CCl4
All Cl-C-Cl bond angles are equal to 109.28° in the CCl4 molecule due to its symmetrical tetrahedral shape.
Conversely, all four C-Cl bond lengths equal 178 pm in the carbon tetrachloride molecule.
As per Pauling’s electronegativity scale, a polar covalent bond is formed between two dissimilar atoms having an electronegativity difference between 0.4 to 1.6 units.
In CCl4, a high electronegativity difference of 0.61 units is present between the covalently bonded carbon (E.N = 2.55) and chlorine (E.N = 3.16) atoms in each C-Cl bond.
Thus all four C-Cl bonds are individually polar in the CCl4 molecule.
Chlorine, being more electronegative, strongly attracts the C-Cl electron cloud largely towards itself. The Cl-atoms thus gain a partial negative charge (δ–), while the central C-atom obtains a partial positive charge (δ+) in CCl4.
However, it is due to the symmetrical tetrahedral shape of CCl4 that the equal and opposite C-Cl dipole moments get canceled completely.
The charged electron cloud stays uniformly distributed; thus, the CCl4 molecule is overall non-polar (net µ = 0).
The Lewis dot structure of carbon tetrachloride (CCl4) displays a total of 32 valence electrons i.e., 32/2 = 16 electron pairs.
Out of the 16 electron pairs, there are 4 bond pairs and 12 lone pairs of electrons.
A C-atom is present at the center of the CCl4 Lewis structure, surrounded by 4 Cl-atoms at the sides.
There is no lone pair of electrons on the central C-atom, while each terminal Cl-atom carries 3 lone pairs, respectively.
How many lone pairs are present in the CCl4 Lewis structure?
Each Cl-atom contains 3 lone pairs of electrons in the CCl4 molecule. Therefore, the total number of lone pairs in CCl4 = 3 x 4 = 12 lone pairs.
What is the molecular shape of CCl4?
The molecular shape of CCl4 w.r.t the central C-atom is tetrahedral.
It is identical to its ideal electron geometry as there is no lone pair of electrons on the central C-atom, so no lone pair-lone pair or lone pair-bond pair electronic repulsions exist in the molecule.
Consequently, there is no distortion witnessed in its shape and/or geometry.
Why is CCl4 non-polar while CCl2F2 is a polar molecule, although both possess a similar tetrahedral shape?
In CCl4, all four bonds present are equivalent; thus, it is a symmetrical tetrahedral molecule. The dipole moments of individually polar C-Cl bonds get canceled equally in opposite directions to yield an overall non-polar molecule (net µ = 0).
Contrarily, CCl2F2 possesses an asymmetric tetrahedral shape; the unequal C-Cl and C-F dipole moments do not get canceled uniformly. Hence, dichlorodifluoromethane (CCl2F2) is overall polar (net µ > 0).
Which of the following molecules possesses a trigonal planar shape?
A) NCl3
B) CCl4
C) BCl3
D) ClF3
Option C is the correct answer. Boron trichloride (BCl3) possesses a trigonal planar shape. To a B-atom at the center, 3 Cl-atoms are single covalently bonded. There is no lone pair of electrons on the central boron atom hence no distortion is expected in the overall molecular shape.
In contrast, the shape of:
NCl3 is trigonal pyramidal. 1 lone pair of electrons is present on the central nitrogen atom.
CCl4is tetrahedral.
ClF3is T-shaped. The central chlorine atom has 2 lone pairs of electrons.
What is the difference between the molecular shapes of CCl4 and CCl2?
The shape of CCl4is tetrahedral, while CCl2 is a bent, angular or V-shaped molecule w.r.t the central C-atom.
There is a lone pair of electrons on the central C-atom in CCl2, which leads to strong lone pair-bond pair electronic repulsions, thus distorting its overall molecular shape and geometry. The Cl-atoms tilt away from the center such that the molecule occupies a bent shape.
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The bond angles of CCl4
