NBr3 Lewis Structure

NBr₃ (nitrogen tribromide) has one nitrogen atom and three bromine atoms. In the lewis structure of NBr₃, there are three single bonds around the nitrogen atom, with three bromine atoms attached to it. Each bromine atom has three lone pairs, and the nitrogen atom has one lone pair.

Steps

Here’s how you can draw the NBr₃ 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

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

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

Since NBr₃ has one nitrogen atom and three bromine atoms, so…

Valence electrons of one nitrogen 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 nitrogen is less electronegative than bromine, assume that the central atom is nitrogen.

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

• And finally, draw the rough sketch

#2 Mark Lone Pairs

Here, we have a total of 13 electron pairs. And three N — 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 nitrogen is a period 2 element, so it can not 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 nitrogen, there is one lone pair.

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

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

Here, both nitrogen 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 (nitrogen) forms an octet. Hence, the octet rule is satisfied.

Therefore, this structure is the stable lewis structure of NBr₃.

Next: CHO₂^– Lewis Structure