HCP 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.

HCP lewis structure has a Carbon atom (C) at the center which is surrounded by one Hydrogen atom (H) and one Oxygen atom (O). There is a triple bond between the Carbon (C) & Phosphorus (P) atom and a single bond between Carbon (C) & Hydrogen (H) atom. There is 1 lone pair on the Phosphorus atom (P).

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

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

Steps of drawing HCP lewis structure

Step 1: Find the total valence electrons in HCP molecule

In order to find the total valence electrons in HCP molecule, first of all you should know the valence electrons present in hydrogen atom, carbon atom as well as phosphorus 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 hydrogen, carbon as well as phosphorus using a periodic table.

Total valence electrons in HCP molecule

→ Valence electrons given by hydrogen atom:

Hydrogen is group 1 element on the periodic table. ^[1] 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.

→ Valence electrons given by carbon atom:

Carbon is group 14 element on the periodic table. ^[2] Hence the valence electrons present in carbon is 4.

You can see the 4 valence electrons present in the carbon atom as shown in the above image.

→ Valence electrons given by phosphorus atom:

Phosphorus is group 15 element on the periodic table. ^[3] 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.

Hence, 

Total valence electrons in HCP molecule = valence electron given by 1 hydrogen atom + valence electrons given by 1 carbon atom + valence electrons given by 1 phosphorus atom = 1 + 4 + 5 = 10.

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 HCP and it contains hydrogen atom (H), carbon atom (C) and phosphorus atom (P).

So as per the rule we have to keep hydrogen outside.

Now, you can see the electronegativity values of carbon atom (C) and phosphorus atom (P) in the above periodic table.

If we compare the electronegativity values of carbon (C) and phosphorus (P) then the carbon atom is less electronegative.

So here the carbon atom (C) is the center atom and the phosphorus atom (P) is the outside atom.

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

Now in the HCP molecule, you have to put the electron pairs between the carbon (C) & hydrogen (H) atom and between the carbon (C) & phosphorus (P) atom.

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

Step 4: Make the outer atoms stable

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

Here in the sketch of HCP molecule, you can see that the outer atoms are hydrogen atom and phosphorus atom.

These hydrogen and phosphorus atoms are forming a duplet and octet respectively and hence they are stable. 

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

The HCP molecule has a total 10 valence electrons and all these valence electrons are used in the above sketch of HCP.

Hence there are no remaining electron pairs to be kept on the central atom. 

So now let’s proceed to the next step.

Step 5: Check the octet on the central atom. If it does not have octet, then shift the lone pair to form a double bond or triple bond.

In this step, you have to check whether the central carbon atom (C) is stable or not.

In order to check the stability of the central carbon (C) atom, we have to check whether it is forming an octet or not.

Unfortunately, the carbon atom is not forming an octet here. Carbon has only 4 electrons and it is unstable.

Now to make this carbon atom stable, you have to shift the electron pair from the outer phosphorus atom so that the carbon atom can have 8 electrons (i.e octet).

But after shifting one electron pair, the carbon atom is still not forming an octet as it has only 6 electrons.

So again we have to shift one more electron pair from the phosphorus atom.

After shifting this electron pair, the central carbon atom will get 2 more electrons and thus its total electrons will become 8.

You can see from the above picture that the carbon atom is forming an octet.

And hence the carbon atom is stable.

Now let’s proceed to the final step to check whether the lewis structure of HCP 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 HCP.

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 hydrogen (H) atom, carbon (C) atom as well as phosphorus (P) atoms present in the HCP 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 HCP molecule in the image given below.

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

For Carbon (C) atom:
Valence electrons = 4 (because carbon is in group 14)
Bonding electrons = 8
Nonbonding electrons = 0

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

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

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

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

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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