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.

Contents

Steps

Here’s how you can easily draw the PI5 Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms

Now, let’s take a closer look at each step mentioned above.

#1 Draw a rough skeleton structure

• 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

• 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

#2 Mention lone pairs on the atoms

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:

#3 If needed, mention formal charges on the atoms

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.

In the above structure, you can see that the central atom (phosphorus) forms an octet. And the outside atoms (iodines) also form an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable Lewis structure of PI5.