ClO3- Lewis structure

ClO₃^– (chlorate) has one chlorine atom and three oxygen atoms.

In the ClO₃^– Lewis structure, there are two double bonds and one single bond around the chlorine atom, with three oxygen atoms attached to it. The oxygen atom with double bonds has two lone pairs, the oxygen atom with a single bond has three lone pairs, and the chlorine atom has one lone pair.

Also, there is a negative (-1) charge on the oxygen atom with a single bond.

Alternative method: Lewis structure of ClO₃^–

Rough sketch

• First, determine the total number of valence electrons

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

Hence, chlorine has seven valence electrons and oxygen has six valence electrons.

Since ClO₃^– has one chlorine atom and three oxygen atoms, so…

Valence electrons of one chlorine atom = 7 × 1 = 7
Valence electrons of three oxygen atoms = 6 × 3 = 18

Now the ClO₃^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 7 + 18 + 1 = 26

Learn how to find: Chlorine valence electrons and Oxygen valence electrons

• Second, find the total electron pairs

We have a total of 26 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 = 26 ÷ 2 = 13

• Third, determine the central atom

We have to place the least electronegative atom at the center.

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

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

• And finally, draw the rough sketch

Lone pair

Here, we have a total of 13 electron pairs. And three Cl — O bonds are already marked. So we have to only mark the remaining ten electron pairs as lone pairs on the sketch.

Also remember that 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.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are oxygens.

So for each oxygen, there are three lone pairs, and for chlorine, there is one lone pair.

Mark the lone pairs on the sketch as follows:

Formal charge

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

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

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

For each oxygen atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both chlorine and oxygen atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both chlorine and oxygen atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

Convert a lone pair of the oxygen atom to make a new Cl — O bond with the chlorine atom as follows:

Since there are charges on chlorine and oxygen atoms, again convert a lone pair of the oxygen atom to make a new Cl — O bond with the chlorine atom as follows:

Final structure

The final structure of ClO₃^– has a central chlorine atom connected to two oxygen atoms via double bonds and to a third oxygen atom via a single bond. In this configuration, the chlorine atom utilizes an expanded octet and retains one lone pair, while the single-bonded oxygen carries three lone pairs and the two double-bonded oxygens each carry two lone pairs. This arrangement represents the most stable state because it minimizes the formal charges of the atoms, leaving a -1 charge only on the single-bonded oxygen atom. Consequently, this geometry serves as the most accurate and stable Lewis representation of the chlorate ion.

To complete the representation, draw square brackets around the entire Lewis structure and place a “-” or “-1” sign as a superscript outside the upper right bracket. This notation signifies that the negative charge is a property of the whole chlorate ion.

Next: HCl Lewis structure

External video

• ClO3- Lewis Structure – How to Draw the Lewis Structure for ClO3- (Chlorate Ion) – YouTube • Wayne Breslyn

External links

• https://www.chemistryscl.com/general/lewis-structure-of-ClO3-/
• https://techiescientist.com/clo3-lewis-structure/
• https://geometryofmolecules.com/clo3-lewis-structure-molecular-geometry-hybridization-shape/
• https://lambdageeks.com/clo3-lewis-structure/
• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/ClO3-lewis-structure.html