P4 (phosphorus) has four phosphorus atoms. In the lewis structure of P4, there are six single bonds between the four phosphorus atoms, and on each phosphorus atom, there is one lone pair.
Here’s how you can draw the P4 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. 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
- 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
#2 Mark Lone Pairs
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:
#3 Mark Charges
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.
And in the above structure, you can see that the central atom (center phosphorus) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of P4.
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