NS2 Lewis structure

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NS₂ has one nitrogen atom and two sulfur atoms.

In NS₂ Lewis structure, there is one single bond and one double bond around the nitrogen atom, with two sulfur atoms attached to it. The sulfur atom with a single bond has three lone pairs, the sulfur atom with a double bond has two lone pairs, and the nitrogen atom has one unpaired electron.

Also, there is a positive (+1) charge on the nitrogen atom, and a negative (-1) charge on the sulfur atom with a single bond.

Steps

Use these steps to correctly draw the NS₂ Lewis structure:

#1 First draw a rough sketch
#2 Mark lone pairs on the atoms
#3 Calculate and mark formal charges on the atoms, if required
#4 Convert lone pairs of the atoms, and minimize formal charges
#5 Repeat step 4 if needed, until all charges are minimized, to get a stable Lewis structure

Let’s discuss each step in more detail.

#1 First draw a rough sketch

• First, determine the total number of valence electrons

In the periodic table, nitrogen lies in group 15, and sulfur lies in group 16.

Hence, nitrogen has five valence electrons and sulfur has six valence electrons.

Since NS₂ has one nitrogen atom and two sulfur atoms, so…

Valence electrons of one nitrogen atom = 5 × 1 = 5
Valence electrons of two sulfur atoms = 6 × 2 = 12

And the total valence electrons = 5 + 12 = 17

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

• Second, find the total electron pairs

We have a total of 17 valence electrons. And when we divide this value by two, we get the value of total electron pairs.

But 17 can not be divided by two. Hence, there are a total of 8 electron pairs and one unpaired electron.

• Third, determine the central atom

We have to place the least electronegative atom at the center.

Since sulfur is less electronegative than nitrogen, the central atom should be sulfur, right?

But if we place sulfur in the center and nitrogen outside, 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.

Hence, here we have to assume that the central atom is nitrogen.

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

• And finally, draw the rough sketch

#2 Mark lone pairs on the atoms

Here, we have 8 electron pairs and one unpaired electron. And two N — S bonds are already marked. So we have to only mark the remaining six electron pairs and one unpaired electron 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 sulfur 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 sulfurs.

So for each sulfur, there are three lone pairs, and for nitrogen, there is one unpaired electron.

Mark the lone pairs on the sketch as follows:

#3 Calculate and mark formal charges on the atoms, if required

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 – 1 – ½ (4) = +2

For each sulfur atom, formal charge = 6 – 6 – ½ (2) = -1

Here, both nitrogen and sulfur atoms have charges, so mark them on the sketch as follows:

The above structure is not a stable Lewis structure because both nitrogen and sulfur atoms have charges. Therefore, reduce the charges (as below) by converting lone pairs to bonds.

#4 Convert lone pairs of the atoms, and minimize formal charges

Convert a lone pair of the sulfur atom to make a new N — S bond with the nitrogen atom as follows:

In the above structure, you can see that the central atom (nitrogen) doesn’t form an octet. And there are still charges on the atoms.

But we can not convert a lone pair to a bond because nitrogen can not keep more than 8 electrons in its last shell. So no need to worry about the octet rule here.

The formal charges on atoms are closer to zero. Also, the above structure is more stable than the previous structures. Therefore, this structure is the most stable Lewis structure of NS₂.

Next: SiH₂O Lewis structure

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External links

• https://lambdageeks.com/ns2-lewis-structure/
• https://www.chegg.com/homework-help/questions-and-answers/draw-lewis-structure-ns2-molecule-indicate-formal-charges-x-isan–edit-structure–q87172540
• https://www.bartleby.com/questions-and-answers/determine-a-possible-lewis-structure-for-ns2-and-whether-it-has-diamagnetic-or-paramagnetic-property/76a446cb-921e-468b-8e4e-b84e94f5cb6e
• https://oneclass.com/homework-help/chemistry/7028545-ns2-lewis-structure.en.html