P2H4 Lewis structure

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P2H4 Lewis Structure
P2H4 Lewis structure

P2H4 (diphosphane) has two phosphorus atoms and four hydrogen atoms.

In P2H4 Lewis structure, there is a single bond between the two phosphorus atoms, and each phosphorus is attached with two hydrogen atoms, and on each phosphorus atom, there is one lone pair.


Here’s how you can easily draw the P2H4 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
Periodic table

In the periodic table, phosphorus lies in group 15, and hydrogen lies in group 1.

Hence, phosphorus has five valence electrons and hydrogen has one valence electron.

Since P2H4 has two phosphorus atoms and four hydrogen atoms, so…

Valence electrons of two phosphorus atoms = 5 × 2 = 10
Valence electrons of four hydrogen atoms = 1 × 4 = 4

And the total valence electrons = 10 + 4 = 14

  • Second, find the total electron pairs

We have a total of 14 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 = 14 ÷ 2 = 7

  • Third, determine the central atom

Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.

Now there are only two atoms remaining and both atoms are phosphorus, so we can assume any one as the central atom.

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

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

  • And finally, draw the rough sketch
P2H4 Lewis Structure (Step 1)
Rough sketch of P2H4 Lewis structure

#2 Mention lone pairs on the atoms

Here, we have a total of 7 electron pairs. And five bonds are already marked. So we have to only mark the remaining two 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 hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are hydrogens and right phosphorus. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for each phosphorus, there is one lone pair.

Mark the lone pairs on the sketch as follows:

P2H4 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of P2H4

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

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

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

In the above structure, you can see that the central atom (left phosphorus) forms an octet. The outside atom (right phosphorus) also forms an octet, and all hydrogens form a duet. Hence, the octet rule and duet rule are satisfied.

Therefore, this structure is the stable Lewis structure of P2H4.

Next: SI6 Lewis structure

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