CCl4 is the chemical formula for the colorless, sweet-smelling liquid called carbon tetrachloride, also sometimes known as tetrachloromethane.
Tetra means four so by carbon tetrachloride we understand that four chlorine atoms are attached to a carbon in this molecule.
The question that we are here to address is whether CCl4 is polar or nonpolar in nature. So, let us find out immediately.
Carbon tetrachloride (CCl4) is a non-polar molecule. There are four C-Cl polar bonds present in CCl4. The polarity of each bond is attributed to a significant electronegativity difference between the two bonded atoms.
The whole molecule however is non-polar due to its symmetric, tetrahedral shape. Thus, CCl4 is a non-polar molecule overall with a net dipole moment, µ =0.
The answer given above makes us think about the following three factors that control the polarity of molecules:
To make things easier for you, we have discussed the role of all three factors in turning out CCl4 as a non-polar molecule in the section below.
Factors affecting the polarity of CCl4
Electronegativity
Chlorine (Cl) is a halogen present in group VII-A (or group 17) of the Periodic Table. It has 7 valence electrons, so it is extremely hungry to gain one more electron and achieve a stable, octet electronic configuration.
This extreme electron affinity is called the high electronegativity of chlorine.
Electronegativity is the ability of an elemental atom to attract a shared pair of electrons from a covalent bond.
Atom | Electronic configuration | Valence electrons |
Carbon (6C) | 1s2 2s2 2p2 | 4 |
Chlorine (17Cl) | 1s2 2s2 2p63s23p5 | 7 |
All covalent bonds with electronegativity differences greater than 0.5 between bonded atoms are essentially polar in nature. Greater the electronegativity difference, the higher the bond polarity. |
Cl (E.N= 3.16) is more electronegative than C (E.N= 2.55). Due to the high electronegativity of Cl, chlorine strongly attracts the shared electron cloud from each C-Cl bond in the CCl4 molecule.
There is an electronegativity difference of 3.16 – 2.55 = 0.61 units.
Therefore, the shift of the C-Cl shared electron cloud toward the chlorine atom to a larger extent develops oppositely charged poles in the CCl4 molecule.
Chlorine gains a partial negative (Clδ-) charge due to a slight excess of electrons. While each carbon atom develops a partial positive charge (Cδ+) due to slight electron deficiency.
Thus, each C-Cl bond in the CCl4 molecule is individually a polar bond. This is called the bond polarity of CCl4.
Dipole moment
The dipole moment is a vector quantity that represents the polarity of a bond and/or a molecule.
The charge separation is measured from the center of the positive pole to the center of the negative pole, technically the bond length.
Q is measured in Coulombs (C) while r is calculated in the unit of distance i.e., meters (m). So, 1 Debye (D) dipole moment = 3.335 X 1030 C.m.
The dipole moment of each C-Cl bond in the CCl4 molecule points from Cδ+ to Clδ-. It has a µ value approximately equal to the electronegativity difference between the bonded atoms.
Molecular geometry
Each C-Cl bond in the CCl4 molecule is polar with a specific dipole moment value, this makes us wonder why is then CCl4 a non-polar molecule overall.
Well, here is where there is a dominant role of this third very important factor i.e., the geometry and shape of the CCl4 molecule.
In CCl4, 4 chlorine atoms are bonded to a carbon atom in the center through single covalent bonds. Each Cl shares 1 valence electron while the C atom shares all 4 of its valence electrons for bond formation.
In this way, all the bonded atoms achieve an octet configuration in the CCl4 molecule.
According to the Valence Shell Electron Pair Repulsion (VSEPR) theory of chemical bonding, CCl4 is an AB4-type molecule.
One atom of C (A), and four atoms of Cl are bonded (B). There is no lone pair on the central A atom.
Thus, CCl4 has a symmetric, tetrahedral geometry or shape.
The net dipole moment effect of three C-Cl bonds, pointing downwards (blue arrow) gets canceled with the dipole moment of a C-Cl bond, pointing upwards in the tetrahedron (red arrow).
This cancelation of dipole moments in opposite directions makes CCl4 a non-polar molecule overall with a net dipole moment value µ=0. CCl4 has a mutual bond angle of 109.5 °.
Examples Of Polar Molecules
As previously mentioned, water is a polar molecule. The bonds that exist between the oxygen atoms and hydrogen atoms are distributed such that both sides of the atom, both of the oxygen-hydrogen and bonds, are evenly spaced. The result is that the oxygen side, or top of the molecule, has a slightly negative charge while the hydrogen atoms, or the bottom of the molecule, has a slightly positive charge.
Ethanol is a polar molecule because the oxygen atoms that are within the molecule have more electronegativity than the other atoms. The oxygen atoms attract more electrons due to their higher electronegativity potential, and the -OH bond groups in the molecule have negative charges overall, even if the negative charge is a very slight one.
Other examples of polar molecules include sulfur dioxide (SO2), hydrogen sulfide (H2S) and ammonia (NH3).
Be warned that a molecule can be comprised of polar bonds and yet still be nonpolar. An example is carbon dioxide, which has four bonds yet the dipole moments of the molecule end up neutralizing one another so the molecule is nonpolar.
Difference between polar and non-polar molecules
Polar molecule | Non-polar molecule |
Atoms having a difference in electronegativity | Atoms may have the same or different electronegativity values |
Unequal charge distribution overall | Equal charge distribution overall |
Net dipole moment greater than 0 | Net dipole moment equals to zero |
Examples include water (H2O), hydrogen sulfide (H2S), ammonia (NH3) and sulfur dioxide (SO2), etc., | Examples include oxygen (O2), nitrogen (N2), methane (CH4), and carbon tetrachloride (CCl4). |
FAQ
Is CCl4 a dipole dipole attraction?
What type of dipole is CCl4?
How is CCl4 polar?