PI3 Lewis structure

PI₃ (phosphorus triiodide) has one phosphorus atom and three iodine atoms.

In PI₃ Lewis structure, there are three single bonds around the phosphorus atom, with three iodine atoms attached to it. Each iodine atom has three lone pairs, and the phosphorus atom has one lone pair.

Alternative method: Lewis structure of PI₃

Contents

Rough sketch

First, determine the total number of valence electrons

In the periodic table, phosphorus lies in group 15, and iodine lies in group 17.

Hence, phosphorus has five valence electrons and iodine has seven valence electrons.

Since PI₃ has one phosphorus atom and three iodine atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of three iodine atoms = 7 × 3 = 21

And the total valence electrons = 5 + 21 = 26

Learn how to find: Phosphorus valence electrons

Second, find the total electron pairs

We have a total of 26 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

Total electron pairs = total valence electrons ÷ 2

So the total electron pairs = 26 ÷ 2 = 13

Third, determine the central atom

We have to place the least electronegative atom at the center.

Since phosphorus is less electronegative than iodine, assume that the central atom is phosphorus.

Therefore, place phosphorus in the center and iodines on either side.

And finally, draw the rough sketch

PI3 Lewis Structure (Step 1) — Rough sketch of PI₃ Lewis structure | Image: Learnool

Lone pair

Here, we have a total of 13 electron pairs. And three P — I bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

Also remember that phosphorus is a period 3 element, so it can keep more than 8 electrons in its last shell. And iodine is a period 5 element, so it can keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are iodines.

So for each iodine, there are three lone pairs, and for phosphorus, there is one lone pair.

Mark the lone pairs on the sketch as follows:

PI3 Lewis Structure (Step 2) — Lone pairs marked, and got the stable Lewis structure of PI₃ | Image: Learnool

Formal charge

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For phosphorus atom, formal charge = 5 – 2 – ½ (6) = 0

For each iodine atom, formal charge = 7 – 6 – ½ (2) = 0

Here, both phosphorus and iodine atoms do not have charges, so no need to mark the charges.

Final structure

The final structure of PI₃ comprises a central phosphorus atom linked to three iodine atoms through single covalent bonds. In this arrangement, the phosphorus atom satisfies the octet rule by forming three bonds and retaining one lone pair, while each iodine atom fulfills the octet rule by maintaining three lone pairs of its own. This specific configuration is the most stable because it results in formal charges of zero for every atom in the molecule, representing the most energetically favorable state for the substance. Consequently, this electronic pattern serves as the definitive and most accurate Lewis representation of phosphorus triiodide.

Next: NOBr Lewis structure

External video

PI3 Lewis Structure: How to Draw the Lewis Structure for PI3 (Phosphorus Triiodide) – YouTube • Wayne Breslyn

External links

Deep

Learnool.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.