Lewis structure of PCl3

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The Lewis structure of PCl₃ contains three single bonds, with phosphorus in the center, and three chlorines on either side. There are three lone pairs on each chlorine atom, and one lone pair on the phosphorus atom.

Steps

By using the following steps, you can easily draw the Lewis structure of PCl₃:

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… phosphorus is a group 15 element and chlorine is a group 17 element. Hence, phosphorus has five valence electrons and chlorine has seven valence electrons.

Now PCl₃ has one phosphorus atom and three chlorine atoms.

So the total number of valence electrons = valence electrons of phosphorus atom + (valence electrons of chlorine atom × 3)

Therefore, the total number of valence electrons = 5 + 21 = 26

• Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for phosphorus and chlorine as follows:

Electronegativity value of phosphorus = 2.19
Electronegativity value of chlorine = 3.16

Obviously, phosphorus is less electronegative than chlorine. Hence, assume that phosphorus is the central atom.

So now, put phosphorus in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of PCl₃ something like this:

Also read: How to draw Lewis structure of SF₆ (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since phosphorus is surrounded by three chlorines, use six electrons to show three chemical bonds as follows:

Also read: How to draw Lewis structure of CH₃OH (4 steps)

#3 Mark lone pairs

As calculated earlier, we have a total of 26 valence electrons. And in the above structure, we have already used six valence electrons. Hence, twenty valence electrons are remaining.

Two valence electrons represent one lone pair. So twenty valence electrons = ten lone pairs.

Note that both (phosphorus and chlorine) are the period 3 elements, so they can keep more than 8 electrons in their last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are chlorines, so each chlorine will get three lone pairs. And the central atom (phosphorus) will get one lone pair.

So the Lewis structure of PCl₃ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (phosphorus), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of PH₃ (4 steps)

#4 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

• For phosphorus atom

Valence electrons = 5
Nonbonding electrons = 2
Bonding electrons = 6

Formal charge = 5 – 2 – ½ (6) = 0

• For each chlorine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of PCl₃ looks something like this:

In the above structure, you can see that the formal charges of both (phosphorus and chlorine) are zero. Therefore, this is the stable Lewis structure of PCl₃.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Related

• Lewis structure of SF₆
• Lewis structure of CH₃OH
• Lewis structure of PH₃
• Lewis structure of XeF₂
• Lewis structure of N₂O

External links

• PCl3 (Phosphorus Trichloride) Lewis Structure – Chemistry School
• PCl3 lewis structure, molecular geometry, bond angle, hybridization – Topblogtenz
• PCl3 Lewis Structure in 6 Steps (With Images) – Pediabay
• How to Draw the Dot Structure for PCl3 – The Geoexchange
• Draw the Lewis structure for PCl3 – Homework.Study.com
• PCl3 Lewis Structure, Geometry – Kemicalinfo
• PCl3 Lewis Structure, Hybridization, Molecular Geometry, and MO Diagram – Techiescientist
• What is the Lewis dot structure of PCl3? – Quora
• How to draw PCl3 Lewis Structure? – Science Education and Tutorials
• Phosphorus Trichloride, PCl3 Molecular Geometry & Polarity – Tutor-Homework.com
• Lewis Dot of Phosphorus Trichloride PCl3 – Kent’s Chemistry
• PCl3 Molecular Electron Geometry, Lewis Structure, Bond Angles and Hybridization – Geometry of Molecules
• Lewis Structure of PCl3 – Laurence Lavelle
• Draw the Lewis structure of PCl3 on paper – Chegg
• What is the electron dot structure for PCl3? – Socratic
• Lewis structure for PCl3 – Brainly
• Draw the complete Lewis structure of phosphorus trichloride, PCl3 – Numerade
• Draw the Lewis structure for PCl3 – Bartleby
• PCl3 Geometry and Hybridization – Chemistry Steps