Lewis structure of Br3-

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The Lewis structure of Br₃^– contains two single bonds between the three bromine atoms, and each bromine atom has three lone pairs.

Plus, there is a negative (-1) charge on the center bromine atom.

Steps

By using the following steps, you can easily draw the Lewis structure of Br₃^–.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

• Let’s calculate the total number of valence electrons

We know that… bromine is a group 17 element. Hence, bromine has seven valence electrons.

Now Br₃^– has three bromine atoms.

So the total number of valence electrons = valence electrons of bromine atom × 3

And Br₃^– has a negative (-1) charge, so we have to add one more electron.

Therefore, the total number of valence electrons = 21 + 1 = 22

• Now decide the central atom

There are three bromine atoms in Br₃^–. Hence, we can assume any one as the central atom. Let’s assume that center bromine is the central atom.

So now, put three bromines next to each other. And draw the rough skeleton structure for the Lewis structure of Br₃^– something like this:

Also read: How to draw Lewis structure of SeF₆ (4 steps)

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since center bromine is surrounded by two other bromines, use four electrons to show two chemical bonds as follows:

Also read: How to draw Lewis structure of Br₂ (4 steps)

#3 Mark lone pairs

As calculated earlier, we have a total of 22 valence electrons. And in the above structure, we have already used four valence electrons. Hence, eighteen valence electrons are remaining.

Two valence electrons represent one lone pair. So eighteen valence electrons = nine lone pairs.

Note that bromine is a period 4 element, so it can keep more than 8 electrons in its last shell.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are left bromine and right bromine, so left bromine and right bromine will get three lone pairs. And the central atom (center bromine) will also get three lone pairs.

So the Lewis structure of Br₃^– looks something like this:

In the above structure, you can see that the octet is completed on the central atom (center bromine), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

Also read: How to draw Lewis structure of H₂Se (4 steps)

#4 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

Collect the data from the above structure and then, write it down below as follows:

• For left bromine and right bromine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

• For center bromine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 4

Formal charge = 7 – 6 – ½ (4) = -1

Mention the formal charges of atoms on the structure. So the Lewis structure of Br₃^– looks something like this:

In the above structure, you can see that the formal charges of atoms are closer to zero. Therefore, this is the most stable Lewis structure of Br₃^–.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

Now Br₃^– is an ion having a negative (-1) charge, so draw brackets around the above Lewis structure and mention that charge on the top right corner. And then, the Lewis structure of Br₃^– looks something like this:

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Related

• Lewis structure of SeF₆
• Lewis structure of Br₂
• Lewis structure of H₂Se
• Lewis structure of COF₂
• Lewis structure of NO₂F

External links

• Chemical Bonding: Br3- Lewis Structure – The Geoexchange
• Br3- Lewis Structure in 5 Steps (With Images) – Pediabay
• Br3- Lewis Structure, Characteristics:13 Must To Know Facts – Lambda Geeks
• what is the lewis structure of br3- – Chegg
• Use Lewis structures to explain why Br3- and I3- are stable, while F3- is not – Pearson
• What is the Lewis structure of Br₃^– ion? – Quizlet
• Use lewis structures to explain why br3- and i3- are stable, while f3- is not – Brainly
• what is the lewis structure for Br3- – Course Hero
• Use Lewis structures to explain why Br3 – and I3- are stable, while F3 – is not – Bartleby