Lewis structure of AlCl3

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The Lewis structure of AlCl₃ contains three single bonds, with aluminum in the center, and three chlorines on either side. There are three lone pairs on each chlorine atom, and the aluminum atom does not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of AlCl₃.

#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… aluminum is a group 13 element and chlorine is a group 17 element. Hence, aluminum has three valence electrons and chlorine has seven valence electrons.

Now AlCl₃ has one aluminum atom and three chlorine atoms.

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

Therefore, the total number of valence electrons = 3 + 21 = 24

• 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 aluminum and chlorine as follows:

Electronegativity value of aluminum = 1.61
Electronegativity value of chlorine = 3.16

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

So now, put aluminum in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of AlCl₃ something like this:

Also read: How to draw Lewis structure of CH₂F₂ (4 steps)

#2 Show chemical bond

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

Also read: How to draw Lewis structure of CH₃^– (4 steps)

#3 Mark lone pairs

As calculated earlier, we have a total of 24 valence electrons. And in the above structure, we have already used six valence electrons. Hence, eighteen valence electrons are remaining.

Two valence electrons represent one lone pair. So eighteen valence electrons = nine lone pairs.

Note that both (aluminum 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 (aluminum) will not get any lone pair, because all nine lone pairs are used.

So the Lewis structure of AlCl₃ looks something like this:

In the above structure, you can see that the octet is completed on outside atoms. But, the central atom (aluminum) doesn’t form an octet.

Now aluminum has an exception in AlCl₃, that it does not require eight electrons to complete its octet.

So 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 NH₂^– (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 aluminum atom

Valence electrons = 3
Nonbonding electrons = 0
Bonding electrons = 6

Formal charge = 3 – 0 – 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 AlCl₃ looks something like this:

In the above structure, you can see that the formal charges of both (aluminum and chlorine) are zero. Therefore, this is the stable Lewis structure of AlCl₃.

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

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Related

• Lewis structure of CH₂F₂
• Lewis structure of CH₃^–
• Lewis structure of NH₂^–
• Lewis structure of acetone
• Lewis structure of NI₃

External links

• AlCl3 Lewis Structure in 5 Steps (With Images) – Pediabay
• AlCl3 lewis structure, molecular geometry, bond angle, polarity, electrons – Topblogtenz
• Aluminium chloride (AlCl3) lewis structure – Chemistry School
• AlCl3 Lewis Structure, Molecular Structure, Hybridization, Bond Angle, and Shape – Geometry of Molecules
• How to draw AlCl3 Lewis Structure? – Science Education and Tutorials
• AlCl3 Lewis Structure & Characteristics: 15 Complete Facts – Lambda Geeks
• Aluminum Trichloride, AlCl3 Molecular Geometry & Polarity – Tutor-Homework.com
• AlCl3 Lewis Structure, Geometry – Kemicalinfo
• Draw the Lewis dot structure of AlCl3 – Homework.Study.com
• Draw the Lewis Structure for AlCl3 – Chegg
• What is the structure of the ALCL3? – Quora
• Draw the Lewis dot structure for AlCl3 – Bartleby
• What is the Lewis structure for the compound aluminum chloride, AlCl3? – OneClass