Lewis structure of AsCl3

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The Lewis structure of AsCl₃ contains three single bonds, with arsenic in the center, and three chlorines on either side. There are three lone pairs on each chlorine atom, and one lone pair on the arsenic atom.

Steps

By using the following steps, you can easily draw the Lewis structure of AsCl₃.

#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… arsenic is a group 15 element and chlorine is a group 17 element. Hence, arsenic has five valence electrons and chlorine has seven valence electrons.

Now AsCl₃ has one arsenic atom and three chlorine atoms.

So the total number of valence electrons = valence electrons of arsenic 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 arsenic and chlorine as follows:

Electronegativity value of arsenic = 2.18
Electronegativity value of chlorine = 3.16

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

So now, put arsenic in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of AsCl₃ something like this:

Also read: How to draw Lewis structure of XeH₄ (4 steps)

#2 Show chemical bond

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

Also read: How to draw Lewis structure of BeI₂ (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 arsenic is a period 4 element, so it can keep more than 8 electrons in its last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its 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 (arsenic) will get one lone pair.

So the Lewis structure of AsCl₃ looks something like this:

In the above structure, you can see that the octet is completed on the central atom (arsenic), 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 SiCl₂Br₂ (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 arsenic 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 AsCl₃ looks something like this:

In the above structure, you can see that the formal charges of both (arsenic and chlorine) are zero. Therefore, this is the stable Lewis structure of AsCl₃.

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

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Related

• Lewis structure of XeH₄
• Lewis structure of BeI₂
• Lewis structure of SiCl₂Br₂
• Lewis structure of POCl₃
• Lewis structure of SOCl₂

External links

• Drawing the Lewis Structure for AsCl3 (Arsenic Trichloride) – The Geoexchange
• AsCl3 Lewis Structure in 6 Steps (With Images) – Pediabay
• What is the molecular geometry of AsCl3? – Socratic
• How to draw AsCl3 Lewis Structure? – Science Education and Tutorials
• Draw the Lewis dot structure for AsCl3 – Homework.Study.com
• Draw the Lewis structure for AsCl3 where As is the central atom – Chegg
• based on the lewis structure, the number of electron groups in the valence shell of the arsenic atom in the ascl3 molecule is – Brainly
• The Lewis structure for AsCl3 shows – Bartleby