Is PF5 a polar or nonpolar compound?

Phosphorus Pentafluoride is another name for the chemical compound PF5. It’s one of the most important phosphorus halides in the planet. PF5 is a colourless, poisonous gas that emits fumes into the atmosphere. It is extremely harmful to the eyes and produces nausea when inhaled. We will investigate if PF5 is a polar or nonpolar chemical in this article.

Is PF5 polar or nonpolar, then? Because of its symmetrical structure (Trigonal Bipyramidal), phosphorus pentafluoride, or PF5, is a nonpolar molecule. Although the P-F bond is polar because the F atom is more electronegative than the P atom, the entire PF5 molecule is nonpolar because the dipoles of the P-F bond cancel each other out, resulting in a nonpolar molecule with zero net dipole moment.

It exists as a noxious odourless molecule that emits very harmful vapours into the atmosphere. When the hydrolysis process occurs, it responds violently.

By nature, PF5 is strongly reactive to water, forming phosphoric and hydrofluoric acid, with phosphoric acid resulting from an exothermic reaction that produces heat.

Fluorination of phosphorus pentachloride with arsenic trifluoride is a simple way to make this PF5 chemical.

3PCl5    +     5AsF3    ā€”ā€”>     3PF5    +     5AsCl

The fluorination of PCl3 with anhydrous hydrofluoric acid in the presence of chlorine can also be used to make PF5. This procedure assures a high rate of PF5 conversations.

Why is PF5 a nonpolar compound?

In both the vertical and horizontal axes of the Phosphorous Pentafluoride molecule, the electron pull balances out electronegativity.

One of the PF5 molecule’s axes is straight, while the other takes on a triangular shape, resulting in no net dipole moment.

Because the dipole moment created by each P-F bond is cancelled, the molecule has no dipole charge.

Phosphorous Pentafluoride (PF5) has a trigonal bipyramidal chemical shape.

Around the core element Phosphorous, PF5 has a symmetric charge distribution of Fluorine atoms.

This molecule is nonpolar because the charge distribution is equal and there is no net dipole moment.

The dipole of P-F bonds is cancelled out by each other due to the symmetric structure of the complete PF5 molecule, despite the fact that the P-F bond is polar in nature due to differences in electronegativity.

Points to consider while determining the polarity of PF5.

In general, the bonds in a nonpolar molecule have equal electronegativity in the participating atoms.

However, if atoms are organised in such a way that the polar bond vector sum cancels out, the molecule becomes nonpolar.

The bonds in PF5 are symmetric, however the molecule possesses polar bonds negating their vector sum because the electronegativity of fluorine is larger than that of the phosphorus atom.

Because there is no dipole moment and no lone pair of electrons, this cancellation is responsible for the nonpolar aspect of the system.

As a result, PF5 takes on a trigonal bipyramidal shape with a pair of equatorial and axial linkages.

The molecule has no net charge because the charges of the horizontal and vertical bonds cancel each other out.

Because there is no net charge on the molecule, it is nonpolar and forms polar covalent bonds.

Phosphorus Pentafluoride Hybridization (PF5)

If we look at this molecule’s Lewis structure!

The phosphorus atom in PF5 has a total of 5 valence electrons, while fluorine’s outermost shell has 7 electrons. Each fluorine atom shares one electron to complete its octet.

In the periodic table, the elements in the third period have d orbitals as well as s and p orbitals.

The fact that all 90-degree and 120-degree bond angles formed in trigonal bipyramidal geometry are not similar is striking.

As a result, the 5 sp3d orbitals of phosphorus and the p orbitals of fluorine atoms overlap. All five Pā€“F sigma bonds in PF5 are formed by these p orbitals, which are uniquely occupied.

As a result, the PF5 molecule exhibits a trigonal bipyramidal geometric form with an sp3d hybridization.

Phosphorus Pentafluoride’s Dipole Moment

The electronegativity of both atoms, phosphorus and fluorine, is different. The fluorine atom has an electronegativity of 3.98, while phosphorus has an electronegativity of 2.19.

As a result, the P-F bond is polar.

Because of the trigonal bipyramidal shape of the molecule, the polarity of the P-F polar bonds cancels out.

There is no charge distribution unevenly because the molecule Phosphorus Pentafluoride (PF5) is symmetrically organised around the core (P) atom.

As a result, PF5 has no net (zero) dipole moment.

CBr4 (Carbon tetrabromide) is a related chemical that has polar C-Br bonds with some dipole moment value but is nonpolar overall due to the net-zero dipole.

Look into the polarity of CBr4 in this article.

Even having an odd number of vectors around the centre atom, why is PF5 nonpolar?

This is due to PF5’s three-dimensional structure (i.e. ball and stick diagram).

Because F has a higher electronegative value than P, the bonds produced in PF5 are polar, but the molecule is nonpolar overall. Why?

Because the F atoms in PF5 are arranged in a trigonal bipyramidal molecular shape, electrons are evenly distributed.

As a result, even with an odd number of vectors, no dipole charge is created, and the Compound PF5 is nonpolar.

BCl3, a nonpolar compound with an odd number of vectors around a central atom, is one such element with an odd number of vectors.

The PF5 Ball and Stick Model is shown below.

Why is it that PF5 is a gas (covalent) yet PCl5 is an ionic solid?

Phosphorus is a common atom in both molecules, but the halogen is different in each.

The valence electrons of chlorine and fluorine are the same, although the fluorine atom is smaller than chlorine.

As a result, fluorine has a higher electron density than chlorine, resulting in a lower polarising factor and a more ionic character in PCl5.

Fluorine, on the other hand, is a smaller atom with a higher electron density, which results in a more polarising and covalent nature, and it exists in gaseous form.

Why is PF5 referred described as a hazardous or toxic substance?

Due to its intense reactivity with water, this colourless Phosphorus Pentafluoride is considered a very toxic chemical.

When inhaled, it is highly poisonous and destructive to human skin. It is caustic to the eyes and skin, causing eye injury.

To avoid contact with water or even humidity, Phosphorus Pentafluoride (PF5) should be stored in sealed steel cylinders.

When the substance comes into contact with water, an exothermic reaction occurs, releasing deadly fumes as well as enough heat to burn any combustible material.

As a result, it’s a potentially hazardous chemical that reacts aggressively to hydrolysis.

Conclusion

The fluorinating agent phosphorus pentafluoride is employed in a variety of industrial chemical processes. Because of its symmetric geometrical structure, the chemical is nonpolar. The core phosphorus atom is symmetrically surrounded by all five fluorine atoms. Inhaling it is dangerous. The dipole moment of PF5 is zero. It’s a nonpolar chemical that forms polar covalent bonds.

Read more: Is Diamond a Mineral or an Element?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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