The **Lewis structure of I**_{3}** ^{–}** contains two single bonds between the three iodine atoms, and each iodine atom has three lone pairs.

Plus, there is a negative (-1) charge on the center iodine atom.

## Steps

By using the following steps, you can easily draw the Lewis structure of I_{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… iodine is a group 17 element. Hence, iodine has **seven** valence electrons.

Now I_{3}^{–} has three iodine atoms.

So the total number of valence electrons = valence electrons of iodine atom × 3

And I_{3}^{–} has a negative (-1) charge, so we have to add one more electron.

Therefore, the **total number of valence electrons** = 21 + 1 = 22

- Now decide the central atom

There are three iodine atoms in I_{3}^{–}. Hence, we can assume any one as the central atom. Let’s assume that **center iodine is the central atom**.

So now, put three iodines next to each other. And draw the rough skeleton structure for the Lewis structure of I_{3}^{–} something like this:

**Also read:** How to draw Lewis structure of BCl_{3} (4 steps)

### #2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since center iodine is surrounded by two other iodines, use four electrons to show **two chemical bonds** as follows:

**Also read:** How to draw Lewis structure of CN^{–} (5 steps)

### #3 Mark lone pairs

As calculated earlier, we have a total of 22 valence electrons. And in the above structure, we have already used four valence electrons. Hence, eighteen valence electrons are remaining.

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

Note that iodine is a period 5 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 left iodine and right iodine, so left iodine and right iodine will get three lone pairs. And the central atom (center iodine) will also get three lone pairs.

So the Lewis structure of I_{3}^{–} looks something like this:

In the above structure, you can see that the octet is completed on the central atom (center iodine), 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 CF_{4} (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
**left iodine**and**right iodine**atom

Valence electrons = 7

Nonbonding electrons = 6

Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

- For
**center iodine**atom

Valence electrons = 7

Nonbonding electrons = 6

Bonding electrons = 4

Formal charge = 7 – 6 – ½ (4) = -1

Mention the formal charges of atoms on the structure. So the Lewis structure of I_{3}^{–} looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the **most stable Lewis structure of I**_{3}** ^{–}**.

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

Now I_{3}^{–} is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of I_{3}^{–} looks something like this:

## Related

- Lewis structure of BCl
_{3} - Lewis structure of CN
^{–} - Lewis structure of CF
_{4} - Lewis structure of PF
_{3} - Lewis structure of XeF
_{4}

## External video

- I3- Lewis Structure – How to Draw the Lewis Structure for I3- – Wayne Breslyn

## External links

- Lewis Structure for I3- – The University of Maryland
- I3- Lewis Structure: Drawings, Hybridization, Shape, Charges, Pairs – Lambda Geeks
- I3- Lewis Structure in 5 Steps (With Images) – Pediabay
- I3- lewis structure, molecular geometry, bond angle, hybridization – Topblogtenz
- I3 Lewis Structure, Molecular Geometry, Hybridization, Polarity, and MO Diagram – Techiescientist
- Draw the Lewis structure for I3-. For this molecule, determine the molecular geometry, electron domain geometry, bond angles, and hybridization about the central atom – Homework.Study.com
- I3- Lewis Structure, Shape, Hybridization and Polarity – Geometry of Molecules
- Chemical Bonding: I3- Lewis Structure – The Geoexchange
- Lewis Dot of Triiodide Ion I3- – Kent’s Chemistry
- I3- Lewis Structure (Triiodide) – Pinterest
- Lewis Structure for I3- – Laurence Lavelle
- Triiodide ion (I3-) – Lewis Structure – Chemistry School
- (I3)- Lewis dot structure. Why would this structure not resonate as I shown, sharing the center Iodine’s negative charge with the outside iodines? – Reddit
- What is the shape of triiodide (I3-)? – Quora
- How is the structure of triiodide ion (I3-) possible? – Chemistry Stack Exchange
- Draw the Lewis structure for I3- . Is the molecule polar or nonpolar? – Bartleby
- Draw The Lewis Structure For I3- – Chegg
- What is the lewis structure of I3-? – Brainly
- Please explain the Lewis structure of the I3- ion, which is hypervalent. Where do we obtain ions and all things in this way? – Numerade
- Draw the Lewis structure for I3- – OneClass

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.