NCl3 (nitrogen trichloride) has one nitrogen atom and three chlorine atoms. In the lewis structure of NCl3, there are three single bonds around the nitrogen atom, with three chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the nitrogen atom has one lone pair.
Here’s how you can draw the NCl3 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, nitrogen has five valence electrons and chlorine has seven valence electrons.
Since NCl3 has one nitrogen atom and three chlorine atoms, so…
Valence electrons of one nitrogen atom = 5 × 1 = 5
Valence electrons of three chlorine 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 chlorine, assume that the central atom is nitrogen.
Therefore, place nitrogen in the center and chlorines 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 — Cl 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 chlorine is a period 3 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 chlorines.
So for each chlorine, 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 chlorine atom, formal charge = 7 – 6 – ½ (2) = 0
Here, both nitrogen and chlorine 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 NCl3.
Next: CHCl3 Lewis Structure