HOCl Lewis Structure

HOCl Lewis Structure

HOCl (hypochlorous acid) has one hydrogen atom, one oxygen atom, and one chlorine atom. In the lewis structure of HOCl, there are two single bonds around the oxygen atom, with hydrogen and chlorine atoms attached to it. The oxygen atom has two lone pairs, and the chlorine atom has three lone pairs.


Here’s how you can draw the HOCl lewis structure step by step.

Step #1: draw sketch
Step #2: mark lone pairs
Step #3: mark charges (if there are)

Let’s break down each step in detail.

#1 Draw Sketch

  • First, determine the total number of valence electrons

In the periodic table, hydrogen lies in group 1, oxygen lies in group 16, and chlorine lies in group 17.

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

Since HOCl has one hydrogen atom, one oxygen atom, and one chlorine atom, so…

Valence electrons of one hydrogen atom = 1 × 1 = 1
Valence electrons of one oxygen atom = 6 × 1 = 6
Valence electrons of one chlorine atom = 7 × 1 = 7

And the total valence electrons = 1 + 6 + 7 = 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 we have to choose the central atom from oxygen and chlorine. Place the least electronegative atom at the center.

Since chlorine is less electronegative than oxygen, the central atom should be chlorine, right?

But if we place chlorine in the center and hydrogen and oxygen on either side, and calculate the formal charge, then we do not get the formal charges on atoms closer to zero.

And the structure with the formal charges on atoms closer to zero is the best lewis structure.

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

Therefore, place oxygen in the center and hydrogen and chlorine on either side.

  • And finally, draw the rough sketch
HOCl Lewis Structure (Step 1)

#2 Mark Lone Pairs

Here, we have a total of 7 electron pairs. And two bonds are already marked. So we have to only mark the remaining five 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. 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.

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

So for chlorine, there are three lone pairs, and for oxygen, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

HOCl Lewis Structure (Step 2)

#3 Mark Charges

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 oxygen atom, formal charge = 6 – 4 – ½ (4) = 0

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

Here, the atoms do not have charges, so no need to mark the charges.

And in the above structure, you can see that the central atom (oxygen) forms an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable lewis structure of HOCl.

Next: NH2Cl Lewis Structure

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