Lewis structure of Cl-

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Cl^– (chloride) has one chlorine atom.

In the Lewis structure of Cl^–, there are four lone pairs on the chlorine atom. Also, there is a negative (-1) charge on the chlorine atom.

Steps

Use these steps to correctly draw the Lewis structure of Cl^–:

#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

In the periodic table, chlorine lies in group 17. Hence, chlorine has seven valence electrons.

Since Cl^– has one chlorine atom, so…

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

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

So the total valence electrons = 7 + 1 = 8

Learn how to find: Chlorine valence electrons

• 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

There is only one atom present here, so assume that the central atom is chlorine.

• And finally, draw the rough sketch

#2 Mark lone pairs on the atoms

Here, we have a total of 4 electron pairs. So we have to mark these four 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.

Always start to mark the lone pairs from outside atoms. But here, there is no outside atom. So for chlorine, there are four lone pairs.

Mark the lone pairs on the sketch as follows:

#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 chlorine atom, formal charge = 7 – 8 – ½ (0) = -1

Here, the chlorine atom has a charge, so mark it on the sketch as follows:

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

Now there is still a negative (-1) charge on the chlorine atom.

This is okay, because the structure with a negative charge on the most electronegative atom is the best Lewis structure. And in this case, the most electronegative element is chlorine.

Therefore, this structure is the most stable Lewis structure of Cl^–.

And since the Cl^– has a negative (-1) charge, mention that charge on the Lewis structure by drawing brackets as follows:

Next: C₅H₁₂ Lewis structure

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