PI5 Lewis structure

PI₅ (phosphorus pentaiodide) has one phosphorus atom and five iodine atoms.

In PI₅ Lewis structure, there are five single bonds around the phosphorus atom, with five iodine atoms attached to it, and on each iodine atom, there are three lone pairs.

Alternative method: Lewis structure of PI₅

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 PI₅ has one phosphorus atom and five iodine atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of five iodine atoms = 7 × 5 = 35

And the total valence electrons = 5 + 35 = 40

Learn how to find: Phosphorus valence electrons

Second, find the total electron pairs

We have a total of 40 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 = 40 ÷ 2 = 20

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

PI5 Lewis Structure (Step 1) — Rough sketch of PI₅ Lewis structure | Image: Learnool

Lone pair

Here, we have a total of 20 electron pairs. And five P — I bonds are already marked. So we have to only mark the remaining fifteen 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 zero lone pair because all fifteen electron pairs are over.

Mark the lone pairs on the sketch as follows:

PI5 Lewis Structure (Step 2) — Lone pairs marked, and got the stable Lewis structure of PI₅ | 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 – 0 – ½ (10) = 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 PI₅ features a central phosphorus atom connected to five iodine atoms through single covalent bonds. In this arrangement, the phosphorus atom serves as an exception to the octet rule, utilizing an expanded valence shell to accommodate ten electrons across five bonding pairs. Each iodine atom fulfills its octet by maintaining three lone pairs of its own alongside the single shared bond. This configuration is the most stable because it results in formal charges of zero for all atoms involved, representing the most energetically favorable state for the molecule. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of phosphorus pentaiodide.

Next: SO₂F₂ Lewis structure

External video

How to Draw the Lewis Dot Structure for PI5: Phosphorus pentaiodide – 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.