PF3Cl2 Lewis structure

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PF3Cl2 Lewis Structure
PF3Cl2 Lewis structure

PF3Cl2 (phosphorus trifluorodichloride) has one phosphorus atom, three fluorine atoms, and two chlorine atoms.

In PF3Cl2 Lewis structure, there are five single bonds around the phosphorus atom, with three fluorine atoms and two chlorine atoms attached to it, and each fluorine and chlorine atom has three lone pairs.


Use these steps to correctly draw the PF3Cl2 Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

  • First, determine the total number of valence electrons
Periodic table

In the periodic table, phosphorus lies in group 15, and both fluorine and chlorine lie in group 17.

Hence, phosphorus has five valence electrons, and both fluorine and chlorine have seven valence electrons.

Since PF3Cl2 has one phosphorus atom, three fluorine atoms, and two chlorine atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of three fluorine atoms = 7 × 3 = 21
Valence electrons of two chlorine atoms = 7 × 2 = 14

And the total valence electrons = 5 + 21 + 14 = 40

  • Second, find the total electron pairs

We have a total of 40 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 40 ÷ 2 = 20

  • Third, determine the central atom

We have to place the least electronegative atom at the center.

Since phosphorus is less electronegative than fluorine and chlorine, assume that the central atom is phosphorus.

Therefore, place phosphorus in the center and fluorine and chlorine on either side.

  • And finally, draw the rough sketch
PF3Cl2 Lewis Structure (Step 1)
Rough sketch of PF3Cl2 Lewis structure

#2 Mark lone pairs on the atoms

Here, we have a total of 20 electron pairs. And five bonds are already marked. So we have to only mark the remaining fifteen electron pairs as lone pairs on the sketch.

Also remember that both (phosphorus and chlorine) are the period 3 elements, so they can keep more than 8 electrons in their last shell. And fluorine is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are fluorines and chlorines.

So for each fluorine and each chlorine, there are three lone pairs, and for phosphorus, there is zero lone pair because all fifteen electron pairs are over.

Mark the lone pairs on the sketch as follows:

PF3Cl2 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of PF3Cl2

#3 Calculate and mark formal charges on the atoms, if required

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For phosphorus atom, formal charge = 5 – 0 – ½ (10) = 0

For each fluorine and each chlorine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, the atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (phosphorus) forms an octet. And the outside atoms (fluorines and chlorines) also form an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable Lewis structure of PF3Cl2.

Next: AlCl4 Lewis structure

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