PF3Cl2 Lewis Structure & Characteristics (13 Important Facts)

PF₃Cl₂ or phosphorus dichloride trifluoride is a halogenated compound of phosphorus having a molecular weight of 158.87 g/mol. Let us learn about PF₃Cl₂.

PF₃Cl₂ is a pentavalent molecule of P, the central P is sp³d hybridized here so the geometry is pentagonal pyramidal. The F atoms are present in that part where s character is lesser because F is more electronegative. Two F atoms are present in the axial position and Cl atoms lie at equatorial.

The hybridization of the axial position is pd where zero s character is present and for the equatorial site, it is sp². We should learn about the lewis structure, valence electrons, hybridization, and polarity of the PF₃Cl₂ with proper explanation in the following part of the article.

1.     How to draw PF₃Cl₂ lewis structure?

The lewis structure of PF₃Cl₂ gives us an idea of valence electrons, shape, and bond angle. Let us try to draw the lewis structure of PF₃Cl₂ in a few steps.

Counting the valence electrons

Counting the valence electrons for a molecule is the 1^st step of the lewis structure drawing. The counting of valence electrons is the counting of the individual atoms’ electrons. The total valence electrons for the PF₃Cl₂ are 40, which is the summation of individual atoms.

Choosing the central atom

The 2^nd step for lewis structure drawing is the select the central atoms among all the constituent atoms based on the size and electropositivity. The central atom for PF₃Cl₂ is P because it has larger in size than F and Cl and is also more electropositive than those halogen atoms.

Satisfying the octet

After the successful bond formation, every atom in the PF₃Cl₂ obeys the octet rule by completing its valence orbital. The electrons required for the completion of the octet are 6*8 = 48 because all atoms belong to the p block element. Reaming electrons from the valence electrons are accompanied by bonds.

Satisfying the valency

To complete the octet every atom should satisfy by its stable valency. P has stable valency 5 so it forms five bonds by sharing electrons with five halogen atoms. Where each halogen makes a single bond to satisfy their monovalency. Although P maintains its valency but violates its octet here.

Assign the lone pairs

The remaining valence electrons after bond formation exist as lone pairs over respective atoms. Here each halogen atoms contain three pairs of lone pairs because they have seven valence electrons and their stable valency is one so the remaining electrons exist as lone pairs. But P lacks lone pairs.

2.     PF₃Cl₂ valence electrons

The electrons present in the valence shell or orbital of each atom are involved in the bond formation are known as valence electrons. Let us count the valence electrons for PF₃Cl₂.

The total valence electrons for the PF₃Cl₂ molecule are 40, which is the summation of the valence electron for one P, three F, and two Cl atoms. The valence electrons of the P, F, and Cl are 5,7, and 7 respectively as they belong to groups VA and VIIA by their electronic configuration.

• The valence electrons for the P atom are 5
• The valence electrons for the Cl atoms are 7
• The valence electrons for the F atoms are 7
• So, the overall valence electrons for the PF₃Cl₂ molecule are 5+(7*2) + (7*3) = 40

3.     PF₃Cl₂ lewis structure lone pairs

The non-bonded electrons are present in the valence orbital after the bond formation known as lone pairs. Let us count the lone pairs of the PF₃Cl₂ molecule.

The total number of lone pairs present in the PF₃Cl₂ molecule is 30 which means 15 pairs. Those are the contribution from the F and Cl site because they have excess non-bonded electrons after the bond formation and for the molecule, we just add them together to get the total number of lone pairs. P has not any lone pairs.

• The formula for the calculating lone pair is, lone pairs = valence electrons – bonded electrons.
• The lone pairs over the P atom are, 5-5=0
• The lone pairs over each F atom are, 7-1=6
• The lone pairs over each Cl atom are, 7-1=6
• So, the total lone pairs over the PF₃Cl₂ molecule are, 6*2 + 6*3 = 30 lone pairs

4.     PF₃Cl₂ lewis structure octet rule

Octet is the completion of the valence orbital accepting the suitable number of electrons during the bond formation. Let us see whether PF₃Cl₂ follows octet or not.

In the PF₃Cl₂ molecule, P violates its octet by expanding its coordination number. The stable valency of P are 3 and 5, in this molecule, it is satisfied by its pentavelncy but during the pentavalency, it involved its empty d orbital for the fifth bond formation and shares electrons.

For the p block, element 8 electrons are the maximum allowed for the octet but p share more than eight electrons which is a violation of its octet, actually P has a vacant d orbital involved here. Each halogen atom completes the octet by sharing one electron in the valence orbital.

5.     PF₃Cl₂ lewis structure shape

The lewis structure shape is the molecular shape that can be adopted by the central atom after bond formation with others. Let us discuss the shape of PF₃Cl₂.

The shape of the PF₃Cl₂ molecule is trigonal bipyramidal which can be confirmed by the following table.

From the above VSEPR (Valence Shell Electrons Pair Repulsion) theory, it is confirmed that PF₃Cl₂ is an AX₅ type of molecule and adopts the trigonal bipyramidal geometry. It is the best geometry Penta coordinated molecule if there is no deviation factor present. F atoms lie at the axial position.

6.     PF₃Cl₂ lewis structure angle

The bond angle for a molecule after adopting a particular structure for proper orientation of the molecule is made by atoms. Let us calculate the bond angle for PF₃Cl₂.

The bond angle for the PF₃Cl₂ is 90⁰ and 72⁰ for the axial and equatorial bond angles respectively. Here two types of bond angles are observed for the two types of the orientation of the molecule. Axial bonds are present over pd hybridization where s character is absent and bond angle is 90⁰.

• We can also calculate the bond angle from the hybridization value
• By using bent’s rule COSθ = (p-1)/p predicts the bond angle
• For the pd hybridization, the p character is ½,
• So, the bond angle COSθ = [(1/2)-1]/(1/2)
• Θ = COS^-1(-1) = 180⁰ which is not allowed and subtract 90⁰ so, we get 180⁰-90⁰=90⁰

7.     PF₃Cl₂ lewis structure formal charge

By the concept of formal charge, we can predict if the molecule is neutral or electrically charged by assuming the same electronegativity. Let us calculate the formal charge of PF₃Cl₂.

The formal charge value for PF₃Cl₂ is zero because all the electrical charges are neutralized by the same and opposite charge. P has pentavalent and the other five halogens are monovalent which are equally balanced. Also, the magnitude of cations is neutralized by the anions and possesses a neutral character.

• Let us calculate the formal charge of PF₃Cl₂ by the formula, F.C. = N_v – N_l.p. -1/2 N_b.p
• the formal charge present over the P is, 5-0-(10/2) = 0
• the formal charge present over the F is, 7-6-(2/2) = 0
• the formal charge present over the Cl is, 7-6-(2/2) = 0
• so, the overall formal charge present 0+0+0 = 0

8.     PF₃Cl₂ hybridization

Mixing two atomic orbitals to get a new hybrid orbital of equivalent energy is knowns as hybridization. Let us explore about hybridization of PF₃Cl₂ in detail.

The central P in the PF₃Cl₂ is sp³d hybridized which is confirmed by the following table,

• We can calculate the hybridization by the convention formula, H = 0.5(V+M-C+A),
• So, the hybridization of central P is, ½(5+5+0+0) = 5 (sp³d)
• One s orbital and three p orbitals and one d orbital of P are involved in the hybridization.
• The lone pairs of F and Cl are also involved in the hybridization.

9.     Is PF₃Cl₂ polar or nonpolar?

The polarity of a molecule depends on the presence of the permanent dipole moment. Let us discuss whether PF₃Cl₂ is polar or not.

PF₃Cl₂ is polar because the geometry of the molecule is not symmetrical. There is also an electronegativity difference among three atoms, so when a dipole-moment is created between P and F or P and Cl they are not equal in magnitude. so, a permanent dipole moment is present in the molecule making it polar.

10. Is PF₃Cl₂ electrolyte?

A substance is called an electrolyte when it dissociates in water and carries electricity through the solution. Let us see whether PF₃Cl₂ is an electrolyte or not.

PF₃Cl₂ acts as an electrolyte because in the aqueous solution it gets dissociated to form fluoride and chloride ions, which are highly electronegative in nature. So, the aqueous solution becomes charged and carries electricity very easily. The dissociation occurred partially to get those ions.

11. Is PF₃Cl₂ soluble in water?

Hydrolysis of water by breaking the bond of a molecule to get dissolved in it is known as soluble in water. Let us see whether PF₃Cl₂ is soluble in water or not.

PF₃Cl₂ is soluble in water and the main reason behind this is H-bonding. Because there are two electronegative halogens F and Cl are present and also due to the smaller size they are ideal for better H-bonding. So, when they formed H-bonding with water then they were soluble in water also.

12. Is PF₃Cl₂ solid or gas?

Based on the physical state at room temperature in which state a molecule wants to stay solid or gaseous. Let us check whether it exists as solid or gaseous.

PF₃Cl₂ is a colorless gaseous molecule at room temperature because the van der Waal’s force of attraction in between the molecule is very low, so the atoms are closely bound and apart from each other. So, the density of the molecule becomes very low and exists as a gaseous form.

There is more void space present within the molecule which makes it gaseous at room temperature, but when temperature decreases then the atoms are coming to close and exist as a liquid.

13. Is PF₃Cl₂ ionic or covalent?

According to Fajan’s rule, no molecule has 100% ionic or covalent character it is vice versa based on polarizability. Let us see whether PF₃Cl₂   is covalent or ionic.

As per the bond model of the PF₃Cl_2, we can say that it is a covalent molecule because central P makes five bonds via sharing five electrons with the other substituent atoms. Although the P-F bond is polar they are formed by the sharing of electrons, so the molecule is covalent in nature.

P cannot polarize F and Cl because its ionic potential is very low, again the polarizability of Cl and F are also poor so they cannot be polarized by the cation. So, they have less ionic character and more covalent nature.

Conclusion

PF₃Cl₂ is a covalent polar molecule having geometry pentagonal bipyramidal. Two F atoms are present at the axial position because there is a lesser s character present and according to the bent’s rule, electronegative atoms prefer to bind those site of hybrid orbital where lesser s character is present. The remaining F and two Cl atoms are present at the equatorial site.

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Biswarup Chandra Dey

Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.