PF5 Lewis Structure

PF5 Lewis Structure

PF5 (phosphorus pentafluoride) has one phosphorus atom and five fluorine atoms. In the lewis structure of PF5, there are five single bonds around the phosphorus atom, with five fluorine atoms attached to it, and on each fluorine atom, there are three lone pairs.

Steps

Here’s how you can draw the PF5 lewis structure step by step.

Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges (if there are)

Let’s break down each step in detail.

#1 Draw Sketch

  • First, determine the total number of valence electrons

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

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

Since PF5 has one phosphorus atom and five fluorine atoms, so…

Valence electrons of one phosphorus atom = 5 × 1 = 5
Valence electrons of five fluorine 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 fluorine, assume that the central atom is phosphorus.

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

  • And finally, draw the rough sketch
PF5 Lewis Structure (Step 1)

#2 Mark Lone Pairs

Here, we have a total of 20 electron pairs. And five P — F 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 fluorine is a period 2 element, so it can not keep more than 8 electrons in its last shell.

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

So for each fluorine, 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:

PF5 Lewis Structure (Step 2)

#3 Mark Charges

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 fluorine atom, formal charge = 7 – 6 – ½ (2) = 0

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

And in the above structure, you can see that the central atom (phosphorus) forms an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable lewis structure of PF5.

Next: H2SO4 Lewis Structure

Leave a Comment