P2H4 Lewis Structure in 6 Steps (With Images)

So you have seen the above image by now, right?

Let me explain the above image in short.

P2H4 lewis structure has a single bond between the two Phosphorus atoms (P) as well as between the Phosphorus atom (P) and Hydrogen atom (H). There are 2 lone pairs on both the Phosphorus atoms (P).

If you haven’t understood anything from the above image of P2H4 lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of P2H4.

So let’s move to the steps of drawing the lewis structure of P2H4.

Steps of drawing P2H4 lewis structure

Step 1: Find the total valence electrons in P2H4 molecule

In order to find the total valence electrons in a P2H4 molecule, first of all you should know the valence electrons present in phosphorus atom as well as hydrogen atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)

Here, I’ll tell you how you can easily find the valence electrons of phosphorus as well as hydrogen using a periodic table.

Total valence electrons in P2H4 molecule

→ Valence electrons given by phosphorus atom:

Phosphorus is group 15 element on the periodic table. ^[1] Hence the valence electrons present in phosphorus is 5.

You can see the 5 valence electrons present in the phosphorus atom as shown in the above image.

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[2] Hence the valence electron present in hydrogen is 1.

You can see that only 1 valence electron is present in the hydrogen atom as shown in the above image.

Hence, 

Total valence electrons in P2H4 molecule = valence electrons given by 2 phosphorus atoms + valence electrons given by 4 hydrogen atoms = 5(2) + 1(4) = 14.

Step 2: Select the central atom

For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.

(Remember: If hydrogen is present in the given molecule, then always put hydrogen outside.)

Now here the given molecule is P2H4 and it contains phosphorus atoms (P) and hydrogen atoms (H).

You can see the electronegativity values of phosphorus atom (P) and hydrogen atom (H) in the above periodic table.

If we compare the electronegativity values of phosphorus (P) and hydrogen (H) then the hydrogen atom is less electronegative. But as per the rule we have to keep hydrogen outside.

So here both the phosphorus atoms (P) are the center atom and the hydrogen atoms (H) are the outside atoms.

Step 3: Connect each atoms by putting an electron pair between them

Now in the P2H4 molecule, you have to put the electron pairs between the phosphorus-phosphorus atoms and between the phosphorus-hydrogen atoms.

This indicates that these atoms are chemically bonded with each other in a P2H4 molecule.

Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.

Now in this step, you have to check the stability of the outer atoms.

Here in the sketch of P2H4 molecule, you can see that the outer atoms are hydrogen atoms.

These outer hydrogen atoms are forming a duplet and hence they are stable. 

Also, in step 1 we have calculated the total number of valence electrons present in the P2H4 molecule.

The P2H4 molecule has a total 14 valence electrons and out of these, only 10 valence electrons are used in the above sketch.

So the number of electrons which are left = 14 – 10 = 4.

You have to put these 4 electrons on the phosphorus atoms in the above sketch of P2H4 molecule.

Now let’s proceed to the next step.

Step 5: Check the octet on the central atom

In this step, you have to check whether the central phosphorus atoms (P) are stable or not.

In order to check the stability of the central phosphorus (P) atoms, we have to check whether they are forming an octet or not.

You can see from the above picture that both the phosphorus atoms are forming an octet.

And hence these phosphorus atoms are stable.

Now let’s proceed to the final step to check whether the lewis structure of P2H4 is stable or not.

Step 6: Check the stability of lewis structure

Now you have come to the final step in which you have to check the stability of lewis structure of P2H4.

The stability of lewis structure can be checked by using a concept of formal charge.

In short, now you have to find the formal charge on phosphorus (P) atoms as well as hydrogen (H) atoms present in the P2H4 molecule.

For calculating the formal charge, you have to use the following formula;

Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons

You can see the number of bonding electrons and nonbonding electrons for each atom of P2H4 molecule in the image given below.

For Phosphorus (P) atom:
Valence electrons = 5 (because phosphorus is in group 15)
Bonding electrons = 6
Nonbonding electrons = 2

For Hydrogen (H) atom:
Valence electron = 1 (because hydrogen is in group 1)
Bonding electrons = 2
Nonbonding electrons = 0

From the above calculations of formal charge, you can see that the phosphorus (P) atoms as well as hydrogen (H) atoms have a “zero” formal charge.

This indicates that the above lewis structure of P2H4 is stable and there is no further change in the above structure of P2H4.

In the above lewis dot structure of P2H4, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of P2H4.

I hope you have completely understood all the above steps.

For more practice and better understanding, you can try other lewis structures listed below.

Try (or at least See) these lewis structures for better understanding:

About author

Jay Rana

Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.

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