ClBr3 (chlorine tribromide) has one chlorine atom and three bromine atoms. In the lewis structure of ClBr3, 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.
Here’s how you can draw the ClBr3 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
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 Mark Lone Pairs
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.
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 Mark Charges
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.
And in the above structure, you can see that the central atom (chlorine) forms an octet. Hence, the octet rule is satisfied.
Therefore, this structure is the stable lewis structure of ClBr3.
Next: P2O5 Lewis Structure