PF5 Lewis structure

PF₅ (phosphorus pentafluoride) has one phosphorus atom and five fluorine atoms.

In the PF₅ Lewis structure, 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.

Alternative method: Lewis structure of PF₅

Rough 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

Learn how to find: Phosphorus valence electrons and Fluorine 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 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

Lone pair

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:

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 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.

Final structure

The final structure of PF₅ includes a central phosphorus atom connected to five fluorine atoms through single covalent bonds. In this configuration, the phosphorus atom utilizes an expanded octet to accommodate ten valence electrons across five bonding pairs. Each fluorine atom fulfills its octet by maintaining three lone pairs of its own alongside the single shared bond. This arrangement 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. Consequently, this specific electronic distribution serves as the definitive and most accurate Lewis representation of phosphorus pentafluoride.

Next: H₂SO₄ Lewis structure

External video

• PF5 Lewis Structure – How to Draw the Lewis Structure for PF5 (Phosphorus Pentafluoride) – YouTube • Wayne Breslyn

External links

• https://geometryofmolecules.com/pf5-lewis-structure-molecular-geometry-bond-angle-and-shape/
• https://topblogtenz.com/pf5-lewis-structure-molecular-geometry-bond-angle-hybridization/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/PF5-lewis-structure.html
• https://lambdageeks.com/pf5-lewis-structure/