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.

Alternative method: Lewis structure of AsBr₃

Rough sketch

• First, determine the total number of valence electrons

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

Learn how to find: Arsenic valence electrons and Bromine 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 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

Lone pair

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:

Formal charge

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.

Final structure

The final structure of AsBr₃ consists of a central arsenic atom linked to three bromine atoms through single covalent bonds. In this arrangement, the arsenic atom satisfies the octet rule by forming three bonding pairs and retaining one lone pair. Within this layout, each bromine atom successfully reaches a stable octet by maintaining three lone pairs alongside its single shared bond. This configuration represents the most stable state for the molecule because it results in a formal charge of zero for every atom involved. Therefore, this specific electronic distribution serves as the definitive and most accurate Lewis representation of arsenic tribromide.

Next: TeO₃ Lewis structure

External video

• How to Draw the Lewis Dot Structure for AsBr3: Arsenic tribromide – YouTube • Wayne Breslyn

External links

• https://www.reddit.com/r/chemhelp/comments/gjawm1/how_do_i_draw_the_lewis_dot_structure_for_arsenic/
• https://www.bartleby.com/questions-and-answers/asbr-3-1.-draw-lewis-structure-2.-identify-electronic-geometries-3.-identify-molecular-geometries-4./4c904ddc-ff4f-47cb-85c2-741f012e44d5
• https://www.chegg.com/homework-help/questions-and-answers/draw-lewis-structures-following-compounds-make-certain–structures-follow-octet-ruleb-corr-q86082051