HCl Lewis structure

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HCl Lewis Structure
HCl Lewis structure

HCl (hydrogen chloride) has one hydrogen atom and one chlorine atom.

In the HCl Lewis structure, there is a single bond between hydrogen atom and chlorine atom, and on the chlorine atom, there are three lone pairs.


Use these steps to correctly draw the HCl Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required

Let’s discuss each step in more detail.

#1 First draw a rough sketch

  • First, determine the total number of valence electrons
Periodic table

In the periodic table, hydrogen lies in group 1, and chlorine lies in group 17.

Hence, hydrogen has one valence electron and chlorine has seven valence electrons.

Since HCl has one hydrogen atom and one chlorine atom, so…

Valence electrons of one hydrogen atom = 1 × 1 = 1
Valence electrons of one chlorine atom = 7 × 1 = 7

And the total valence electrons = 1 + 7 = 8

  • Second, find the total electron pairs

We have a total of 8 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 = 8 ÷ 2 = 4

  • 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.

Hence, here we have to assume that the central atom is chlorine.

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

#2 Mark lone pairs on the atoms

Here, we have a total of 4 electron pairs. And one H — Cl bond is already marked. So we have to only mark the remaining three electron pairs as lone pairs on the sketch.

Also remember that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. And chlorine 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 atom is hydrogen. But no need to mark on hydrogen, because hydrogen already has two electrons.

So for chlorine, there are three lone pairs.

Mark the lone pair on the sketch as follows:

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

#3 Calculate and mark formal charges on the atoms, if required

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

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

For chlorine atom, formal charge = 7 – 6 – ½ (2) = 0

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

In the above structure, you can see that the central atom (chlorine) forms an octet. And the outside atom (hydrogen) also forms a duet. Hence, the octet rule and duet rule are satisfied.

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

Next: H2 Lewis structure

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