NCl2- Lewis structure

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NCl₂^– has one nitrogen atom and two chlorine atoms.

In NCl₂^– Lewis structure, there are two single bonds around the nitrogen atom, with two chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the nitrogen atom has two lone pairs.

Also, there is a negative (-1) charge on the nitrogen atom.

Steps

To properly draw the NCl₂^– Lewis structure, follow these steps:

#1 Draw a rough sketch of the structure
#2 Next, indicate lone pairs on the atoms
#3 Indicate formal charges on the atoms, if necessary

Let’s break down each step in more detail.

#1 Draw a rough sketch of the structure

• First, determine the total number of valence electrons

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

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

Since NCl₂^– has one nitrogen atom and two chlorine atoms, so…

Valence electrons of one nitrogen atom = 5 × 1 = 5
Valence electrons of two chlorine atoms = 7 × 2 = 14

Now the NCl₂^– has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 5 + 14 + 1 = 20

Learn how to find: Nitrogen valence electrons and Chlorine valence electrons

• Second, find the total electron pairs

We have a total of 20 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 = 20 ÷ 2 = 10

• 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 Next, indicate lone pairs on the atoms

Here, we have a total of 10 electron pairs. And two N — Cl bonds are already marked. So we have to only mark the remaining eight 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 are two lone pairs.

Mark the lone pairs on the sketch as follows:

#3 Indicate formal charges on the atoms, if necessary

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 – 4 – ½ (4) = -1

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

Here, the nitrogen atom has a charge, so mark it on the sketch as follows:

In the above structure, you can see that the central atom (nitrogen) forms an octet. And the outside atoms (chlorines) also form an octet. Hence, the octet rule is satisfied.

Now there is still a negative (-1) charge on the nitrogen atom.

This is not okay, right? Because the structure with a negative charge on the most electronegative atom is the best Lewis structure. And in this case, the most electronegative element is chlorine.

But if we convert a lone pair of the nitrogen atom to make a new N — Cl bond with the chlorine atom, and calculate the formal charge, then we do not get the formal charges on atoms closer to zero.

And the structure with the formal charges on atoms closer to zero is the best Lewis structure.

Therefore, this structure is the most stable Lewis structure of NCl₂^–.

And since the NCl₂^– has a negative (-1) charge, mention that charge on the Lewis structure by drawing brackets as follows:

Next: AsCl₅ Lewis structure

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External links

• https://www.chegg.com/homework-help/questions-and-answers/lewis-structure-ncl2-q9384605
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