Phosphorus pentafluoride (PF5) lewis dot structure, molecular geometry, hybridization, Bond angle

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pf5 lewis structure molecular geometry

Phosphorous pentafluoride is a toxic and colorless gas, it has the chemical formula of PF5. It has an unpleasant odor.

In this tutorial, we will discuss Phosphorous pentafluoride (PF5) lewis structure, molecular geometry, Bond angle, hybridization, polar or nonpolar, etc.

Phosphorus pentafluoride is soluble in water. It is nonflammable and has zero dipole moment.

Name of MoleculePhosphorous pentafluoride
Chemical formulaPF5
Molecular geometry of PF5Trigonal bipyramidal
Electron geometry of PF5Trigonal bipyramidal
Bond angle 90º and 120º
NatureNonpolar molecule
Total Valence electron in PF540
Overall Formal charge in PF5Zero

How to draw lewis structure of PF5?

PF5 lewis structure is made up of five P-F bonds, with a phosphorus (P) atom in a central position and all five fluorine (F) as outer atoms in the lewis diagram. The lewis structure of PF5 contains a total of 5 bond pairs and 15 lone pairs(3 lone pairs on each fluorine atom).

The drawing of the PF5 lewis’s structure is very easy and simple. Let’s see how to do it.

Steps for drawing the Lewis dot structure for PF5

1. Count total valence electron in PF5

First of all, determine the valence electron that is available for drawing the lewis structure of PF5 because the lewis diagram is all about the representation of valence electrons around atoms.

So, an easy way to find the valence electron of atoms in the PF5 molecule is, just to look at the periodic group of phosphorous and fluorine atoms.

As the phosphorous atom belongs to the 5A group in the periodic table and fluorine is situated in the 7A group, hence, the valence electron for the phosphorous is 5, and for the fluorine atom, it is 7.

⇒ Total number of the valence electron in Phosphorous = 5

⇒ Total number of the valence electrons in fluorine = 7

∴ Total number of valence electron available for the PF5 Lewis structure = 5 + 7×5 = 40 valence electrons         [∴ PF5 molecule has one phosphorous and five fluorine atoms]

valence electrons in pf5 lewis structure

2. Find the least electronegative atom and place it at center

An atom with a less electronegative value is preferable for the central position in the lewis diagram because they are more prone to share the electrons with surrounding atoms.

In the case of the PF5 molecule, the phosphorous atom is less electronegative than the fluorine atom.

Hence, put the phosphorous atom at the central position of the lewis diagram and all five fluorine atoms outside it.

central atom in pf5

3. Connect outer atoms to the central atom with a single bond

In this step, join all outer atoms to the central atom with the help of a single bond.

In, the PF5 molecule, fluorine is the outer atom, and phosphorous is the central atom. Hence, joined them as shown in the figure given below.

pf5 skeletal structure

Count the number of valence electrons used in the above structure. There are 5 single bonds used in the above structure, and one single bond means 2 electrons.

Hence, in the above structure, (5 × 2) = 10 valence electrons are used from a total of 40 valence electrons available for drawing the PF5 Lewis structure.

∴ (40 – 10) = 30 valence electrons

So, we are left with 30 valence electrons more.

4. Place remaining electrons on the outer atom first and complete their octet

Let’s start putting the remaining valence electrons on outer atoms first. In the case of the PF5 molecule, fluorine is the outer atom and each of them needs 8 electrons to have a full octet.

Start putting the remaining electrons on fluorine atoms as dots till they complete their octet.

pf5 lewis dot structure

So, all fluorine atoms in the above structure completed their octet, because all of them have 8 electrons(6 electrons represented as dots + 2 electrons in every single bond) in their outer shell.

Now again count the valence electron in the above structure.

In the above structure, there is 30 electrons are represented as dots + five single bonds that contain 10 electrons means a total of 40 valence electrons is used in the above structure.

Remember, we have a total of 40 valence electrons available for drawing the lewis structure of PF5. And we used all 40 valence electrons in the above structure.

∴ (40 – 40) = 0 valence electrons

So, we don’t have any remaining valence electrons.

Also, if we look at the above structure, the phosphorous atom is attached to five single bonds that means it have 10 electrons.

Note:- A atom that have more than 8 electrons in their valence shell called Expanded octet.

“The octet rule can be ‘expanded’ by some elements by utilizing the d-orbitals found in the third principal energy level and beyond. Sulfur, phosphorus, silicon, and chlorine are common examples of elements that form an expanded octet.”

Let’s check the formal charge for the above structure to verify whether it’s stable or not.

5. Check the stability with the help of a formal charge concept

The lesser the formal charge on atoms, the better the stability of the lewis diagram.

To calculate the formal charge on an atom. Use the formula given below-

formal charge formula for lewis diagram

⇒ Formal charge = (valence electrons – nonbonding electrons –  1/2 bonding electrons)

Let’s count the formal charge for the 4th step structure.

 For fluorine atom

⇒ Valence electrons of fluorine = 7

⇒ Nonbonding electrons on fluorine = 6

⇒ Bonding electrons around fluorine (1 single bond) = 2

∴ (7 – 6 – 2/2) = 0 formal charge on the fluorine atoms.

 For phosphorous atom

⇒ Valence electrons of phosphorous = 5

⇒ Nonbonding electrons on phosphorous = 0

⇒ Bonding electrons around phosphorous (5 single bonds) = 10

∴ (5 – 0 – 10/2) = 0 formal charge on the phosphorous central atom.

phosphorous pentafluoride (PF5) lewis structure

Phosphorous pentafluoride (PF5) Lewis structure

Hence, in the above PF5 lewis structure, all atoms get a formal charge equal to zero.

Therefore, the above lewis dot structure of PF5 is most stable and appropriate in nature.

Also check – 

What are the electron and molecular geometry of PF5?

The molecular geometry of PF5 is a Trigonal Bipyramidal. In PF5, the central atom Phosphorous (P) has no lone pair and is attached to five fluorine (F) atoms, which means, there are 5 regions of electron density and all the regions are bonding.

According to the VSEPR theory, “The maximum distance five regions of electron density can get away from affords a geometry called trigonal bipyramidal”.

PF5 molecular geometry or shape

The molecular geometry or shape of PF5 is a Trigonal bipyramidal. In PF5, the  Phosphorous (P) atom is present at the central position whereas three fluorine atoms are present at the equatorial position and two fluorine atoms at the Axial position. The final arrangement of this molecule (PF5) appears like a Trigonal bipyramidal shape.

“A trigonal bipyramid simply means two pyramid, If you look at above picture, you should be able to see the pyramids relative to the top half and the bottom half of the central atom.”

Now, What is the electron geometry of PF5?

The electron geometry consider bond pair as well lone pair while determining the geometry of any molecule. And molecular goometry only look at bond pairs.

If there is no lone pair on central atom of molecule, then –

Molecular geometry = Electron geometry for that molecule

The electron geometry of PF5 is also Trigonal bipyramidal, because, the phosphorous (P) central atom has zero lone pair, so, only bonded pairs are considered while evaluating its electron geometry.

According to the VSEPR theory, the central atom with five regions of electron density adopts a trigonal bipyramidal electron geometry. Because repulsion is minimum in electron pairs at this position.

Now, a very simple way to determine the electron and molecular geometry of PF5 is the AXN method.

AXN method to determine shape and geometry

AXN is a simple formula that represents the number of the bonded atom and lone pair on the central atom to predict the shape or geometry of the molecule using the VSEPR chart.

AXN notation for PF5 molecule:

  • A denotes the central atom, so, Phosphorous (P) is the central atom in PF5 molecule A = Phosphorous
  • X denotes the bonded atoms to the central atom, Phosphorous (P) is bonded with five fluorine (F) atoms. Therefore, X = 5
  • N represents the lone pair on the central atom, as per PF5 Lewis structure, the Phosphorous central atom has zero lone pair. Hence, N = 0

So, the AXN generic formula for the PF5 molecule becomes AX5N0 or AX5.

As per the VSEPR chart, if a molecule gets AX5 generic formula then its molecular geometry or shape will be a trigonal bipyramidal, and electron geometry will also be trigonal bipyramidal.

Electron geometry and molecular geometry of PF5 as per VSEPR

Therefore, the molecular geometry for PF5 is trigonal bipyramidal and its electron geometry is also trigonal bipyramidal.

Hybridization of PF5

The hybridization of PF5 is Sp3d. Because the steric number of the phosphorous central atom is five.

The formula for calculating the steric number is-

steric number to calculate hybridization

Steric number = (Number of bonded atoms attached to central atom + Lone pair on central atom)

In the case of the PF5 molecule, phosphorous is the central atom that is attached to the five bonded atoms(fluorine) and it has zero lone pair.

Hence, (5 + 0) = 5 is the steric number of central atom phosphorous in the PF5 molecule that gives Sp3d hybridization.

Steric numberHybridization

The bond angle of PF5

There are two types of bonds formed in PF5, the Axial bond and the Equatorial bond.

The axial bonds is slightly longer than equatorial bond since they bear more repulsive interaction force.

In PF5, two P-F bonds are situated at the Axial position where one lies above the equatorial plane and the other below the plane, they make the angle with the plane is 90º.

Also, three P-F bonds are situated at the equatorial position, and all lie in the same plane, they make an angle with each other, and the angle made between them is 120º.

PF5 bond angle

Also check:- How to find bond angle?

Is PF5 polar or nonpolar?

So, Is PF5 polar or nonpolar? The bond in PF5 is polar because the fluorine (F) atom is more electronegative than the phosphorous (P) atom but the overall structure of PF5 is nonpolar because of its symmetrical structure due to which the polarity of P-F bonds gets canceled by each other.

Also check-


How many lone pairs and bond pairs are present in the lewis structure of PF5?

Lone pairs are those represented as dots in the lewis diagram that do not take part in the formation of bonds and are also called nonbonding electrons. Bonding pairs are the pair of electrons that are in a bond. A single bond has one bond pair means 2 bonding electrons. 

By looking at the PF5 Lewis structure, we see, that there are 30 dot electrons means 15 lone pairs present. [∴ 2 dot electrons means one lone pair). And, there are 5 bonded atoms present which contain 10 bonding electrons.

lone pair and bond pair in pf5 lewis structure

Why the molecular geometry of PF5 is Trigonal bipyramidal?

VSEPR theory says that “pairs of electrons(bond and lone pair) repels each other and these electrons occupy such position in space so that repulsion should between them minimum”.

In the case of PF5, there is no lone pair on the central Phosphorous atom, so, what we have, is 5 bonded pairs. These bonded pairs will repel each other and going to push far away from each other.

According to VSEPR theory, the five bonded pairs will have minimum repulsion between them when they are stretched at the corners of a triangular bipyramid.

These five bonded pairs will be divided into two positions in which, two atoms will be in the Axial position, and three atoms in the Equatorial position.

explain pf5 geometry

The original molecular geometry or shape of PF5 will be Trigonal bipyramidal with two fluorine atoms at the Axial position and three fluorine atoms at the Equatorial position.

Also read:

Properties and uses of Phosphorous pentafluoride

  • It appears as a colorless gas.
  • It has a boiling point of −84.6 °C and a melting point of −93.78 °C.
  • It is a nonflammable and toxic gas with a pungent odor.
  • It acts as Lewis acid.
  •  It is used as a polymerization catalyst.

Reactions of Phosphorous pentafluoride

Phosphorous pentafluoride is directly prepared by the reaction of phosphorus pentachloride with arsenic trifluoride.

⇒ 3PCl5 + 5AsF3 → 3PF5 + 5AsCl3


  • The total valence electron is available for drawing the Phosphorous pentafluoride (PF5) Lewis structure is 40.
  • The molecular geometry or shape of PF5 is a Trigonal bipyramidal.
  • In the PF5 Lewis dot structure, a total of 15 lone pairs and 5 bond pairs are present.
  • The electron geometry of PF5 is also Trigonal bipyramidal.
  • The hybridization of phosphorous in PF5 is sp3d. Since its steric number is 5.
  • In PF5, axial atoms(2 P-F bonds) make a 90º angle with the plane, and equatorial atoms(3 P-F bonds) make a 120º angle with each other. 
  • PF5 is nonpolar in nature.
  • The overall formal charge in PF5 is zero.
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