Lewis Structure of AlCl3 (With 5 Simple Steps to Draw!)

Ready to learn how to draw the lewis structure of AlCl3?

Awesome!

Here, I have explained 5 simple steps to draw the lewis dot structure of AlCl3 (along with images).

So, if you are ready to go with these 5 simple steps, then let’s dive right into it!

Lewis structure of AlCl3 contains three single bonds between the Aluminum (Al) atom and each Chlorine (Cl) atom. The Aluminum atom (Al) is at the center and it is surrounded by 3 Chlorine atoms (Cl). The Aluminum atom does not have a lone pair while all three chlorine atoms have three lone pairs each.

Let’s draw and understand this lewis dot structure step by step.

(Note: Take a pen and paper with you and try to draw this lewis structure along with me. I am sure you will definitely learn how to draw lewis structure of AlCl3).

5 Steps to Draw the Lewis Structure of AlCl3

Step #1: Calculate the total number of valence electrons

Here, the given molecule is AlCl3. In order to draw the lewis structure of AlCl3, first of all you have to find the total number of valence electrons present in the AlCl3 molecule.
(Valence electrons are the number of electrons present in the outermost shell of an atom).

So, let’s calculate this first.

Calculation of valence electrons in AlCl3

• For Aluminum: 

Aluminum is a group 13 element on the periodic table. ^[1]

Hence, the valence electrons present in aluminum is 3 (see below image).

• For Chlorine:

Chlorine is a group 17 element on the periodic table. ^[2]

Hence, the valence electron present in chlorine is 7 (see below image).

Hence in a AlCl3 molecule, 

Valence electrons given by Aluminum (Al) atom = 3
Valence electrons given by each Chlorine (Cl) atom = 7
So, total number of Valence electrons in AlCl3 molecule = 3 + 7(3) = 24

Step #2: Select the center atom

While selecting the center atom, always put the least electronegative atom at the center.

(Remember: Fluorine is the most electronegative element on the periodic table and the electronegativity decreases as we move right to left in the periodic table as well as top to bottom in the periodic table). ^[3]

Here in the AlCl3 molecule, if we compare the aluminum atom (Al) and chlorine atom (Cl), then aluminum is less electronegative than chlorine.

So, aluminum should be placed in the center and the remaining 3 chlorine atoms will surround it.

Step #3: Put two electrons between the atoms to represent a chemical bond

Now in the above sketch of AlCl3 molecule, put the two electrons (i.e electron pair) between each aluminum atom and chlorine atom to represent a chemical bond between them.

These pairs of electrons present between the Aluminum (Al) and Chlorine (Cl) atoms form a chemical bond, which bonds the aluminum and chlorine atoms with each other in a AlCl3 molecule.

Step #4: Complete the octet (or duplet) on outside atoms. If the valence electrons are left, then put the valence electrons pair on the central atom

Don’t worry, I’ll explain!

In the Lewis structure of AlCl3, the outer atoms are chlorine atoms.

So now, you have to complete the octet on these chlorine atoms (because chlorine requires 8 electrons to have a complete outer shell).

Now, you can see in the above image that all the chlorine atoms form an octet.

Also, all the 24 valence electrons of AlCl3 molecule (as calculated in step #1) are used in the above structure. So there are no remaining electron pairs.

Hence there is no change in the above sketch of AlCl3.

Let’s move to the next step.

Step #5: Check the stability of lewis structure by calculating the formal charge on each atom

Now, you have come to the final step and here you have to check the formal charge on aluminum atom (Al) as well as each chlorine atom (Cl).

For that, you need to remember the formula of formal charge;

Formal charge = Valence electrons – Nonbonding electrons – (Bonding electrons)/2

• For Aluminum:
  Valence electrons = 3 (as it is in group 13)
  Nonbonding electrons = 0
  Bonding electrons = 6
• For Chlorine:
  Valence electron = 7 (as it is in group 17)
  Nonbonding electrons = 6
  Bonding electrons = 2

Formal charge	=	Valence electrons	–	Nonbonding electrons	–	(Bonding electrons)/2
Al	=	3	–	0	–	6/2	=	0
Cl	=	7	–	6	–	2/2	=	0

So you can see above that the formal charges on aluminum as well as chlorine are “zero”.

Hence, there will not be any change in the above structure and the above lewis structure of AlCl3 is the final stable structure only.

Each electron pair (:) in the lewis dot structure of AlCl3 represents the single bond ( | ). So the above lewis dot structure of AlCl3 can also be represented as shown below.

Related lewis structures for your practice:
Lewis structure of BeH2
Lewis structure of HNO
Lewis structure of NI3
Lewis structure of CH2F2
Lewis structure of CH3-

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