So you have seen the above image by now, right?
Let me explain the above image in short.
NCl2- lewis structure has a Nitrogen atom (N) at the center which is surrounded by two Chlorine atoms (Cl). There is a single bond between the Nitrogen atom (N) and each Chlorine atom (Cl). There is a -1 formal charge on the Nitrogen atom (N).
If you haven’t understood anything from the above image of NCl2- lewis structure, then just stick with me and you will get the detailed step by step explanation on drawing a lewis structure of NCl2- ion.
So let’s move to the steps of drawing the lewis structure of NCl2- ion.
Steps of drawing NCl2- lewis structure
Step 1: Find the total valence electrons in NCl2- ion
In order to find the total valence electrons in NCl2- ion, first of all you should know the valence electrons present in the nitrogen atom as well as chlorine atom.
(Valence electrons are the electrons that are present in the outermost orbit of any atom.)
Here, I’ll tell you how you can easily find the valence electrons of nitrogen as well as chlorine using a periodic table.
Total valence electrons in NCl2- ion
→ Valence electrons given by nitrogen atom:
Nitrogen is a group 15 element on the periodic table.  Hence the valence electrons present in nitrogen is 5.
You can see the 5 valence electrons present in the nitrogen atom as shown in the above image.
→ Valence electrons given by chlorine atom:
Chlorine is group 17 element on the periodic table.  Hence the valence electrons present in chlorine is 7.
You can see the 7 valence electrons present in the chlorine atom as shown in the above image.
Total valence electrons in NCl2- ion = valence electrons given by 1 nitrogen atom + valence electrons given by 2 chlorine atoms + 1 more electron is added due to 1 negative charge = 5 + 7(2) + 1 = 20.
Step 2: Select the central atom
For selecting the center atom, you have to remember that the atom which is less electronegative remains at the center.
Now here the given ion is NCl2- ion and it contains nitrogen atom (N) and chlorine atoms (Cl).
You can see the electronegativity values of nitrogen atom (N) and chlorine atom (Cl) in the above periodic table.
If we compare the electronegativity values of nitrogen (N) and chlorine (Cl) then the nitrogen atom is less electronegative.
So here the nitrogen atom (N) is the center atom and the chlorine atoms (Cl) are the outside atoms.
Step 3: Connect each atoms by putting an electron pair between them
Now in the NCl2 molecule, you have to put the electron pairs between the nitrogen atom (N) and chlorine atoms (Cl).
This indicates that the nitrogen (N) and chlorine (Cl) are chemically bonded with each other in a NCl2 molecule.
Step 4: Make the outer atoms stable. Place the remaining valence electrons pair on the central atom.
Now in this step, you have to check the stability of the outer atoms.
Here in the sketch of NCl2 molecule, you can see that the outer atoms are chlorine atoms.
These outer chlorine atoms are forming an octet and hence they are stable.
Also, in step 1 we have calculated the total number of valence electrons present in the NCl2- ion.
The NCl2- ion has a total 20 valence electrons and out of these, only 16 valence electrons are used in the above sketch.
So the number of electrons which are left = 20 – 16 = 4.
You have to put these 4 electrons on the central nitrogen atom in the above sketch of NCl2 molecule.
Now let’s proceed to the next step.
Step 5: Check the octet on the central atom
In this step, you have to check whether the central nitrogen atom (N) is stable or not.
In order to check the stability of the central nitrogen (N) atom, we have to check whether it is forming an octet or not.
You can see from the above picture that the nitrogen atom is forming an octet. That means it has 8 electrons.
And hence the central nitrogen atom is stable.
Now let’s proceed to the final step to check whether the above lewis structure is stable or not.
Step 6: Check the stability of lewis structure
Now you have come to the final step in which you have to check the stability of lewis structure of NCl2.
The stability of lewis structure can be checked by using a concept of formal charge.
In short, now you have to find the formal charge on the nitrogen atom (N) as well as chlorine atoms (Cl) present in the NCl2 molecule.
For calculating the formal charge, you have to use the following formula;
Formal charge = Valence electrons – (Bonding electrons)/2 – Nonbonding electrons
For Nitrogen (N) atom:
Valence electrons = 5 (because nitrogen is in group 15)
Bonding electrons = 4
Nonbonding electrons = 4
For Chlorine (Cl) atom:
Valence electrons = 7 (because chlorine is in group 17)
Bonding electrons = 2
Nonbonding electrons = 6
From the above calculations of formal charge, you can see that the nitrogen (N) atom has -1 charge and the chlorine atoms have 0 charges.
So let’s keep these charges on the respective atoms in the NCl2 molecule.
This overall -1 charge on the NCl2 molecule is represented in the image given below.
In the above lewis dot structure of NCl2- ion, you can also represent each bonding electron pair (:) as a single bond (|). By doing so, you will get the following lewis structure of NCl2- ion.
I hope you have completely understood all the above steps.
For more practice and better understanding, you can try other lewis structures listed below.
Try (or at least See) these lewis structures for better understanding:
|AsCl5 Lewis Structure
|COBr2 Lewis Structure
|GeF4 Lewis Structure
|Cl2O2 Lewis Structure
|XeI2 Lewis Structure
|PF2Cl3 Lewis Structure
Jay is an educator and has helped more than 100,000 students in their studies by providing simple and easy explanations on different science-related topics. He is a founder of Pediabay and is passionate about helping students through his easily digestible explanations.
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