P4 Lewis structure

P₄ (phosphorus) has four phosphorus atoms.

In the P₄ Lewis structure, there are six single bonds between the four phosphorus atoms, and on each phosphorus atom, there is one lone pair.

Alternative method: Lewis structure of P₄

Rough sketch

• First, determine the total number of valence electrons

In the periodic table, phosphorus lies in group 15. Hence, phosphorus has five valence electrons.

Since P₄ has four phosphorus atoms, so…

Valence electrons of four phosphorus atoms = 5 × 4 = 20

So the total valence electrons = 20

Learn how to find: Phosphorus valence electrons

• Second, find the total electron pairs

We have a total of 20 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 = 20 ÷ 2 = 10

• Third, determine the central atom

Here, there are four atoms and all atoms are phosphorus, so we can assume any one as the central atom.

Let’s assume that the central atom is center phosphorus.

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 10 electron pairs. And six P — P bonds are already marked. So we have to only mark the remaining four 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.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are one top phosphorus and two bottom phosphorus.

So for each phosphorus, there is one lone pair.

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

Here, the atoms do not have charges, so no need to mark the charges.

Final structure

The final structure of P₄ consists of four phosphorus atoms arranged in a tetrahedral geometry, where each atom is linked to the other three through single covalent bonds. In this arrangement, every phosphorus atom satisfies the octet rule by forming three bonds and retaining one lone pair. Within this layout, the bond angles are constrained to 60°, which introduces significant ring strain but allows each atom to achieve a stable valence shell. This configuration represents the most stable state for this specific allotrope because it results in a formal charge of zero for every atom involved. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of white phosphorus.

Next: C₂H₂Cl₂ Lewis structure

External video

• P4 Lewis Structure: How to Draw the Lewis Structure for P4 – YouTube • Wayne Breslyn