Lewis structure of HOCl

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Lewis structure of HOCl
Lewis structure of HOCl | Image: Root Memory

The Lewis structure of HOCl contains two single bonds, with oxygen in the center, and hydrogen and chlorine on either side. There are three lone pairs on the chlorine atom, two lone pairs on the oxygen atom, and the hydrogen atom does not have any lone pair.

Steps

By using the following steps, you can easily draw the Lewis structure of HOCl.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… hydrogen is a group 1 element, oxygen is a group 16 element, and chlorine is a group 17 element. Hence, hydrogen has one valence electron, oxygen has six valence electrons, and chlorine has seven valence electrons.

Now HOCl has one hydrogen atom, one oxygen atom, and one chlorine atom.

So the total number of valence electrons = valence electrons of hydrogen atom + valence electrons of oxygen atom + valence electrons of chlorine atom

Therefore, the total number of valence electrons = 1 + 6 + 7 = 14

  • Now decide the central atom

We can not assume hydrogen as 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.

Therefore, choose the central atom from oxygen and chlorine.

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for oxygen and chlorine as follows:

Electronegativity value of oxygen = 3.44
Electronegativity value of chlorine = 3.16

Obviously, oxygen is less electronegative than chlorine. Hence, assume that oxygen is the central atom.

So now, put oxygen in the center and hydrogen and chlorine on either side. And draw the rough skeleton structure for the Lewis structure of HOCl something like this:

Skeleton structure for Lewis structure of HOCl | Image: Root Memory

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since oxygen is surrounded by hydrogen and chlorine, use four electrons to show two chemical bonds as follows:

Two chemical bonds shown between atoms | Image: Root Memory

#3 Mark lone pairs

As calculated earlier, we have a total of 14 valence electrons. And in the above structure, we have already used four valence electrons. Hence, ten valence electrons are remaining.

Two valence electrons represent one lone pair. So ten valence electrons = five lone pairs.

Note that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. Oxygen is a period 2 element, so it can not keep more than 8 electrons in its last shell. And chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are hydrogen and chlorine. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So chlorine will get three lone pairs. And the central atom (oxygen) will get two lone pairs.

Now draw the Lewis structure of HOCl something like this:

Lone pairs marked on Lewis structure of HOCl | Image: Root Memory

In the above structure, you can see that the octet is completed on the central atom (oxygen), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#4 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

  • For hydrogen atom

Valence electrons = 1
Nonbonding electrons = 0
Bonding electrons = 2

Formal charge = 1 – 0 – ½ (2) = 0

  • For oxygen atom

Valence electrons = 6
Nonbonding electrons = 4
Bonding electrons = 4

Formal charge = 6 – 4 – ½ (4) = 0

  • For chlorine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of HOCl looks something like this:

Formal charges are calculated, and got the stable Lewis structure of HOCl | Image: Root Memory

In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of HOCl.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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