The **Lewis structure of AsF _{3}** contains three single bonds, with arsenic in the center, and three fluorines on either side. There are three lone pairs on each fluorine atom, and one lone pair on the arsenic atom.

## Steps

By using the following steps, you can easily draw the Lewis structure of AsF_{3}.

#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 fluorine is a group 17 element. Hence, arsenic has **five** valence electrons and fluorine has **seven** valence electrons.

Now AsF_{3} has one arsenic atom and three fluorine atoms.

So the total number of valence electrons = valence electrons of arsenic atom + (valence electrons of fluorine 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 fluorine as follows:

Electronegativity value of arsenic = 2.18

Electronegativity value of fluorine = 3.98

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

So now, put arsenic in the center and fluorines on either side. And draw the rough skeleton structure for the Lewis structure of AsF_{3} something like this:

**Also read:** How to draw Lewis structure of NO_{2}Cl (5 steps)

### #2 Show chemical bond

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

**Also read:** How to draw Lewis structure of BeCl_{2} (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 fluorine is a period 2 element, so it can not 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 fluorines, so each fluorine will get three lone pairs. And the central atom (arsenic) will get one lone pair.

So the Lewis structure of AsF_{3} 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 CH_{2}N_{2} (5 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 fluorine**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 AsF_{3} looks something like this:

In the above structure, you can see that the formal charges of both (arsenic and fluorine) are zero. Therefore, this is the **stable Lewis structure of AsF _{3}**.

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

## Related

- Lewis structure of NO
_{2}Cl - Lewis structure of BeCl
_{2} - Lewis structure of CH
_{2}N_{2} - Lewis structure of KrF
_{2} - Lewis structure of N
_{2}F_{2}

## External links

- Drawing the Lewis Structure for AsF3 (Arsenic Trihydride) – The Geoexchange
- AsF3 Lewis Structure in 6 Steps (With Images) – Pediabay
- AsF3 Lewis Structure, Molecular Geometry, Hybridization, Bond Angle and Shape – Geometry of Molecules
- AsF3 Lewis Structure (Arsenic Trifluoride) – Pinterest
- AsF3 Lewis Structure, Geometry: 13 Facts You Should Know – Lambda Geeks
- How to draw AsF3 Lewis Structure? – Science Education and Tutorials
- Arsenic trifluoride – AsF 3 Lewis Structure – Chemistry School
- Draw the Lewis structure for AsF3 – Chegg
- Describe the molecular geometry of AsF3 – Homework.Study.com
- Is AsF3 Polar or Nonpolar? – Science Coverage
- Draw the Lewis structure for AsF3 – OneClass
- What is the Lewis structure of AsF
_{3}molecule? – Quizlet - Determine the central atom in the Lewis structure of AsF3 – Numerade
- AsF3 (Arsenic Trifluoride) Oxidation Number – ChemicalAid

Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.