Lewis structure of AsH3

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The Lewis structure of AsH₃ contains three single bonds, with arsenic in the center, and three hydrogens on either side. There is one lone pair on the arsenic atom, and the hydrogen atom does not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of AsH₃.

#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 hydrogen is a group 1 element. Hence, arsenic has five valence electrons and hydrogen has one valence electron.

Now AsH₃ has one arsenic atom and three hydrogen atoms.

So the total number of valence electrons = valence electrons of arsenic atom + (valence electrons of hydrogen atom × 3)

Therefore, the total number of valence electrons = 5 + 3 = 8

• Now decide the central atom

We can not assume hydrogen as the central atom, because the central atom is bonded with at least two other atoms. And hydrogen has only one electron in its last shell, so it can not make more than one bond.

Hence, assume that arsenic is the central atom.

So now, put arsenic in the center and hydrogens on either side. And draw the rough skeleton structure for the Lewis structure of AsH₃ something like this:

Also read: How to draw Lewis structure of Br₃^– (4 steps)

#2 Show chemical bond

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

Also read: How to draw Lewis structure of SeF₆ (4 steps)

#3 Mark lone pairs

As calculated earlier, we have a total of 8 valence electrons. And in the above structure, we have already used six valence electrons. Hence, two valence electrons are remaining.

And two valence electrons represent one lone pair.

Note that arsenic is a period 4 element, so it can keep more than 8 electrons in its last shell. And hydrogen is a period 1 element, so it can not keep more than 2 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 hydrogens. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So the central atom (arsenic) will get one lone pair.

Now draw the Lewis structure of AsH₃ 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 Br₂ (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 hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of AsH₃ looks something like this:

In the above structure, you can see that the formal charges of both (arsenic and hydrogen) are zero. Therefore, this is the stable Lewis structure of AsH₃.

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

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Related

• Lewis structure of Br₃^–
• Lewis structure of SeF₆
• Lewis structure of Br₂
• Lewis structure of H₂Se
• Lewis structure of COF₂

External links

• Drawing the Lewis Structure for AsH3 (Arsenic Trihydride) – The Geoexchange
• AsH3 Lewis Structure in 6 Steps (With Images) – Pediabay
• AsH3 Lewis Structure, Geometry, Hybridization, and Polarity – Techiescientist
• How to draw AsH3 Lewis Structure? – Science Education and Tutorials
• How many bonded electrons and lone pairs of electrons does AsH₃ have? – Homework.Study.com
• The lewis structure of ash3 shows __________ nonbonding electron pair(s) on as – Brainly
• Lewis dot structure for AsH3 ???? – Chegg
• How many bonding orbitals are there in AsH₃? – Socratic
• In the Lewis dot structure for AsH3, how many dots are on the arsenic? – Numerade
• Draw the Lewis structure for AsH3 – Bartleby
• How many lone pairs are on the central element for the following compound:AsH3 – Pearson
• What is the hybridisation of ASH3? – Quora
• AsH3 (Arsenic Trihydride) Oxidation Number – ChemicalAid