# ClBr3 Lewis structure

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ClBr3 (chlorine tribromide) has one chlorine atom and three bromine atoms.

In the ClBr3 Lewis structure, there are three single bonds around the chlorine atom, with three bromine atoms attached to it. Each bromine atom has three lone pairs, and the chlorine atom has two lone pairs.

Contents

## Steps

To properly draw the ClBr3 Lewis structure, follow these steps:

#1 Draw a rough sketch of the structure
#2 Next, indicate lone pairs on the atoms
#3 Indicate formal charges on the atoms, if necessary

Let’s break down each step in more detail.

### #1 Draw a rough sketch of the structure

• First, determine the total number of valence electrons

In the periodic table, both chlorine and bromine lie in group 17.

Hence, both chlorine and bromine have seven valence electrons.

Since ClBr3 has one chlorine atom and three bromine atoms, so…

Valence electrons of one chlorine atom = 7 × 1 = 7
Valence electrons of three bromine atoms = 7 × 3 = 21

And the total valence electrons = 7 + 21 = 28

• Second, find the total electron pairs

We have a total of 28 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 = 28 ÷ 2 = 14

• Third, determine the central atom

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

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

But if we place bromine in the center and chlorine outside, 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 chlorine.

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

• And finally, draw the rough sketch

### #2 Next, indicate lone pairs on the atoms

Here, we have a total of 14 electron pairs. And three Cl — Br bonds are already marked. So we have to only mark the remaining eleven 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 bromine is a period 4 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 bromines.

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

Mark the lone pairs on the sketch as follows:

### #3 Indicate formal charges on the atoms, if necessary

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 – 4 – ½ (6) = 0

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

Here, both chlorine and bromine atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (chlorine) forms an octet. And the outside atoms (bromines) also form an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable Lewis structure of ClBr3.