AsBr3 Lewis structure

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AsBr3 Lewis Structure
AsBr3 Lewis structure

AsBr3 (arsenic tribromide) has one arsenic atom and three bromine atoms.

In AsBr3 Lewis structure, there are three single bonds around the arsenic atom, with three bromine atoms attached to it. Each bromine atom has three lone pairs, and the arsenic atom has one lone pair.


To properly draw the AsBr3 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
Periodic table

In the periodic table, arsenic lies in group 15, and bromine lies in group 17.

Hence, arsenic has five valence electrons and bromine has seven valence electrons.

Since AsBr3 has one arsenic atom and three bromine atoms, so…

Valence electrons of one arsenic atom = 5 × 1 = 5
Valence electrons of three bromine atoms = 7 × 3 = 21

And the total valence electrons = 5 + 21 = 26

  • 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 arsenic is less electronegative than bromine, assume that the central atom is arsenic.

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

  • And finally, draw the rough sketch
AsBr3 Lewis Structure (Step 1)
Rough sketch of AsBr3 Lewis structure

#2 Next, indicate lone pairs on the atoms

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

Also remember that both (arsenic and bromine) are the period 4 elements, so they can keep more than 8 electrons in their 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 arsenic, there is one lone pair.

Mark the lone pairs on the sketch as follows:

AsBr3 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of AsBr3

#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 arsenic atom, formal charge = 5 – 2 – ½ (6) = 0

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

Here, both arsenic 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 (arsenic) 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 AsBr3.

Next: TeO3 Lewis structure

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