Polarity of Carbon tetrafluoride

What is the molecular geometry of CF4?
What is the molecular geometry of CF4?

Is CF4 polar or non-polar? – Polarity of CF4

CF4 is the chemical formula of carbon tetrafluoride. It is a colorless, odorless gas. It is used as a low-temperature refrigerant and a gaseous insulator. CF4 has a molar mass of 88.00 g/mol.

If you are excited to know about the polarity of carbon tetrafluoride (CF4), which keeps your favorite food chilled inside the refrigerator, that is, whether CF4 is polar or non-polar, then continue reading this article.

Is CF4 polar or non-polar?

Carbon tetrafluoride (CF4) is a non-polar molecule. It consists of one carbon (C) atom and four fluorine (F) atoms. The carbon is kept at the central position, and all fluorine atoms are at the surrounding positions, making a perfectly symmetrical tetrahedral molecular shape and geometry.

An electronegativity difference of 1.43 units exists between the bonded atoms of carbon and fluorine in each C-F bond in CF4.

Thus, each C-F bond is individually polar in CF4 and possesses a specific dipole moment value (symbol µ).

In the CF4 molecule, the highly electronegative fluorine atom more strongly attracts the bonded electrons than the carbon atom in each C-F bond.

However, it is due to the symmetrical tetrahedral shape of the CF4 molecule in the absence of any lone pair of electrons present on the central carbon atom that the individual C-F dipole moments get canceled equally in the molecule.

Hence, the charged electron cloud stays uniformly spread over the molecule, which leads to an overall non-polar CF4 molecule (net µ = 0).

Name of molecule Carbon tetrafluoride (CF4)
Bond type Polar covalent
Molecular geometry Tetrahedral
Polar or Non-polar? Overall Non-polar
Dipole moment 0
Bond angle ∠ F-C-F= 109.5°

What makes a molecule polar or non-polar?

A molecule is polar if there is a non-uniform charge distribution present in it. If the charge distribution gets equally balanced in different parts, then that molecule or molecular ion is considered non-polar.

The following three factors mainly influence the polarity of a molecule:

  • The electronegativity difference between two or more covalently bonded atoms
  • Dipole moment
  • Molecular geometry or shape

Now, let us discuss the effect of the above three factors one by one to prove that carbon tetrafluoride (CF4) is overall a non-polar molecule.

Factors affecting the polarity of CF4

Electronegativity

It is defined as the ability of an elemental atom to attract a shared pair of electrons from a covalent chemical bond.

Electronegativity increases across a period in the Periodic Table while it decreases down the group.

Greater the electronegativity difference between bonded atoms in a molecule, the higher the bond polarity.

Carbon (C) is present in Group IV-A (or 14) of the Periodic Table. The electronic configuration of carbon is 1s2 2s2 2p2. As per the electronic configuration, a C-atom has a total of 4 valence electrons, it is thus short of 4 more electrons that are required so that the carbon atom can achieve a complete octet electronic configuration.

Conversely, fluorine (F) is a halogen present in Group VII-A (or 17) of the Periodic Table. The electronic configuration of a fluorine atom is 1s2 2s2 2p5. According to this electronic configuration, an F-atom has a total of 7 electrons in its valence shell, and it lacks one more electron to complete its octet electronic configuration.

In CF4, the central C-atom is single covalently bonded to four F-atoms. All 4 valence electrons of carbon consumed in covalent bonding denote there is no lone pair on the central C-atom in the CF4 molecule.

However, each of the four F-atoms contains 3 lone pairs of electrons, respectively. In this way, all bonded atoms attain a completely stable octet electronic configuration via lone pairs and chemical bonding in CF4.

Due to the absence of any lone pair of electrons on the central C-atom in CF4, there is no distortion witnessed in the symmetrical tetrahedral shape or geometry of the molecule.

Atom Electronic configuration Valence electrons
Carbon (6C)

1s22s22p2

4
Fluorine (9F) 1s22s22p5 7

Fluorine (F) is the most electronegative element of the Periodic Table. Therefore, a high electronegativity difference of 1.48 units exists between a C-atom (E. N= 2.55) and an F-atom (E. N= 3.98) in each of the four C-F bonds.

Fluorine more strongly attracts the C-F shared electrons from each bond in the carbon tetrafluoride molecule.

Hence, the fluorine atoms with higher electronegativity gain partial negative (Fδ-) charges while the central carbon atom obtains a partial positive (Cδ+) charge, as shown below.

As a result, in CF4, all the C-F bonds are individually polar, with an electronegativity difference of 1.43 units.

Dipole Moment

Dipole moment (μ) is a vector quantity that points from the positive pole to the negative pole of a bond or a molecule.

It is mathematically calculated as a product of the magnitude of charge (Q) and charges separation (r). The dipole moment is expressed in a unit called Debye (D).

The dipole moment of a polar covalent bond conventionally points from the positive centre to the centre of the negative charge.

So in polar bonds of CF4, the dipole moment of each C-F bond points from Cδ+ to Fδ- (as shown below).

Molecular geometry

According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, CF4 is an AX4E0 or AX4 type molecule. To one C-atom at the center (A), four bonded atoms are attached (four F-atoms), and the central C-atom contains no-lone pair (E).

The molecular geometry or shape of CF4 is tetrahedral which is identical to its electron pair geometry. To minimize the electron repulsion and to attain stability in tetrahedral structure, the bonded atoms of the CF4 molecule possess a bond angle of (∠ F-C-F) 109.5°.

Due to the absence of any lone pair of electrons on the central C-atom, CF4 has an identical molecular and electron geometry i.e., tetrahedral. Highly electronegativity F-atoms attract the shared electron cloud from each C-F bond to the same extent. Hence, all four C-F bonds are individually polar.

Still, it is due to the symmetrical tetrahedral shape of CF4 that the overall charged electron cloud stays uniformly distributed as individual C-F dipole moments gets canceled equally on each side of the molecule.

The net dipole moment of three downwards-pointing C-F bonds gets canceled with the dipole moment of an upwards-pointing C-F bond. Consequently, carbon tetrafluoride CF4 is overall a non-polar molecule (net µ = 0).

Difference between polar and nonpolar?

Polar molecule Non-polar molecule
Atoms must have 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 zero Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), phosphorus trifluoride (PF3), nitrogen trifluoride (NF3), etc. Examples include oxygen (O2), nitrogen (N2), methane (CH4), carbon disulfide (CS2), ethane (C2H6), propane (C3H8), Carbon tetrafluoride (CF4), etc.

Also, check –

  • CF4 lewis structure, molecular geometry, bond angle, hybridization
  • How to tell if a molecule is polar or nonpolar?
  • Is CH2Cl2 polar or nonpolar?
  • Is CH3F polar or nonpolar?
  • Is NCl3 polar or nonpolar?
  • Is NO3– polar or nonpolar?
  • Is BrF5 polar or nonpolar?
  • Is SF4 polar or nonpolar?
  • Is CO2 polar or nonpolar?
  • Is NH3 polar or nonpolar?
  • Is SO2 polar or nonpolar?
  • Is SO3 polar or nonpolar?
  • Is H2O polar or nonpolar?
  • Is H2S polar or nonpolar?
  • Is HCN polar or nonpolar?
  • Is CCl4 polar or nonpolar?
  • Is XeF4 polar or nonpolar?
  • Is CH2O polar or nonpolar?
  • Is CHCl3 polar or nonpolar?
  • Is SF6 polar or nonpolar?
  • Is BF3 polar or nonpolar?
  • Is PCl5 polar or nonpolar?
  • Is CH3Cl polar or nonpolar?

FAQ

Why is CF4 a non-polar molecule?

Hence, CF4 is overall a non-polar molecule with µ = 0.

Why does non-polar CF4 contain polar bonds?

Each C-F bond in the carbon tetrafluoride (CF4) molecule is polar due to a high electronegativity difference of 1.43 units between the bonded C-atom (E. N = 2.55) and F-atom (E.N = 3.98).

However, it is due to the symmetrical tetrahedral molecular shape and geometry of the molecule that individual bond polarities get canceled, and CF4 is overall non-polar.

Why is SF4 polar while CF4 is a non-polar molecule?

CF4 is non-polar, while SF4 is a polar molecule because CF4, the central C-atom uses all of its valence electrons for covalent bonding. There is no lone pair on the C-atom, and CF4 has a symmetrical tetrahedral molecular shape.

Consequently, the dipole moments of individually polar C-F bonds get canceled in opposite directions; thus, it (CF4) is non-polar (net dipole moment µ =0).

Contrarily, in SF4 four F-atoms are bonded to an S-atom. A sulfur atom uses 4 of its 6 valence electrons for bonding but still has one lone pair.

The lone pair-bond pair repulsions lead to a distorted asymmetric seesaw shape of the SF4, So, it is overall polar (net dipole moment µ =0.632 D).

Which of the following chemical molecules is polar? i) BF3 ii) CF4 iii) CO2 iv) PF5 v) SF6

All the above five molecules contain polar bonds, but all these are overall non-polar due to their symmetrical shape and geometry that leads to a uniformly distributed charged electron cloud overall (net µ = 0).

BF3 contains polar B-F bonds having an electronegativity difference of 1.94 units between the bonded atoms. The B-F dipole moments get canceled in the trigonal planar shape of the molecule.

An electronegativity difference of 1.43 units exists between polar C-F bonds in CF4. But the C-F dipole moments get canceled in the tetrahedral molecular shape and geometry.

CO2 is linear in shape. An electronegativity difference of 0.89 units exists between polar C=O bonds, but C=O dipole moments get canceled in the symmetrical shape of the molecule overall.

Each P-F bond is individually polar, with an electronegativity difference of 1.79 units between the bonded atoms. PF5 possesses a symmetrical trigonal bipyramidal shape that leads to P-F dipole moment cancellation.

SF6 possesses polar S-F bonds with an electronegativity difference of 1.40 units between the bonded atoms. However, S-F dipole moments get canceled overall in the octahedral shape of the molecule.

Is there a formal charge on the bonded atoms in the CF4 molecule?

Formal charge of an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]

For the central C-atom

∴ Formal charge on the central C-atom = 4 – 0 – 8/2 = 4 – 0 – 4 = 4 – 4 = 0

For F-atoms

∴ Formal charge on each F-atom = 7 – 6 – 2/2 = 7 – 6 – 1 = 7 – 7 = 0

All atoms in the CF4 molecule including carbon and fluorine obtain a formal charge equal to zero, hence overall charge present on the carbon tetrafluoride molecule is Zero i.e., no charge.

Summary

  • Carbon tetrafluoride (CF4) is a non-polar molecule.
  • It consists of four C-F bonds.
  • C-F bonds are highly polar, with an electronegativity difference of 1.43 units between the bonded C-atom (E. N= 2.55) and F-atom (E. N= 3.98).
  • Carbon tetrafluoride CF4 has a tetrahedral molecular and electron geometry with a bond angle of (∠F-C-F) 109.5°.
  • Due to the absence of any lone pair of electrons on the central C-atom, the CF4 molecule has a symmetrical tetrahedral molecular shape.
  • The individual C-F dipole moments get canceled overall due to the symmetrical shape of the molecule. The net dipole moment μ in CF4 is thus 0, so carbon tetrafluoride is overall a non-polar molecule.

Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let’s connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/

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