Lewis structure of I3-

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Lewis structure of I3-
Lewis structure of I3 | Image: Root Memory

The Lewis structure of I3 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 I3:

#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 I3 has three iodine atoms.

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

And I3 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 I3. 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 I3 something like this:

Skeleton structure for Lewis structure of I3 | Image: Root Memory

#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:

Two chemical bonds shown between atoms | Image: Root Memory

#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 I3 looks something like this:

Lone pairs marked on Lewis structure of I3 | Image: Root Memory

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.

#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 I3 looks something like this:

Formal charges are calculated, and got the most stable Lewis structure of I3 | Image: Root Memory

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 I3.

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

Now I3 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 I3 looks something like this:

Lewis structure of I3 showing a negative (-1) charge | Image: Root Memory

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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.

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