Lewis structure of HClO3

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Lewis structure of HClO3
Lewis structure of HClO3

The Lewis structure of HClO3 contains two double bonds and two single bonds, with chlorine in the center, and three oxygens and hydrogen on either side. There are two lone pairs on each oxygen atom, one lone pair on the chlorine 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 HClO3.

#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)
#5 Convert lone pair and calculate formal charge again (if formal charges are not closer to zero)

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

Now HClO3 has one hydrogen atom, one chlorine atom, and three oxygen atoms.

So the total number of valence electrons = valence electrons of hydrogen atom + valence electrons of chlorine atom + (valence electrons of oxygen atom × 3)

Therefore, the total number of valence electrons = 1 + 7 + 18 = 26

  • 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 chlorine and oxygen.

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

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

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

So now, put chlorine in the center and hydrogen and oxygen on either side. And draw the rough skeleton structure for the Lewis structure of HClO3 something like this:

Skeleton structure for Lewis structure of HClO3

#2 Show chemical bond

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

Four chemical bonds shown between atoms

#3 Mark lone pairs

As calculated earlier, we have a total of 26 valence electrons. And in the above structure, we have already used eight valence electrons. Hence, eighteen valence electrons are remaining.

Two valence electrons represent one lone pair. So eighteen valence electrons = nine lone pairs.

Note that hydrogen is a period 1 element, so it can not keep more than 2 electrons in its last shell. Chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell. And oxygen is a period 2 element, so it can not 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 oxygen. But hydrogen can not keep more than 2 electrons in its last shell. Hence, don’t mark the lone pairs on hydrogen.

So top oxygen and left oxygen will get three lone pairs, and right oxygen will get two lone pairs. And the central atom (chlorine) will get one lone pair.

Now draw the Lewis structure of HClO3 something like this:

Lone pairs marked on Lewis structure of HClO3

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

Now 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 chlorine atom

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

Formal charge = 7 – 2 – ½ (6) = +2

  • For top oxygen and left oxygen atom

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

Formal charge = 6 – 6 – ½ (2) = -1

  • For right oxygen atom

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

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of HClO3 looks something like this:

Formal charges are not closer to zero

In the above structure, you can see that the formal charges of atoms are not closer to zero. Therefore, convert lone pair and calculate formal charge again.

#5 Convert lone pair and calculate formal charge again

As mentioned earlier, chlorine is a period 3 element, so it can keep more than 8 electrons in its last shell.

So convert one lone pair from top oxygen atom, and one lone pair from left oxygen atom to make a new bond with the chlorine atom. And then, the Lewis structure of HClO3 looks something like this:

Lone pair of top and left oxygen is converted, and octet is completed on atoms

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

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 chlorine atom

Valence electrons = 7
Nonbonding electrons = 2
Bonding electrons = 10

Formal charge = 7 – 2 – ½ (10) = 0

  • For each oxygen atom

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

Formal charge = 6 – 4 – ½ (4) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of HClO3 looks something like this:

Formal charges are calculated, and got the stable Lewis structure of HClO3

In the above structure, you can see that the formal charges of all atoms are zero. Therefore, this is the stable Lewis structure of HClO3.

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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