SeS2 Lewis structure - Learnool (2024)

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SeS₂ (selenium disulfide) has one selenium atom and two sulfur atoms.

In the SeS₂ Lewis structure, there are two double bonds around the selenium atom, with two sulfur atoms attached to it. Each sulfur atom has two lone pairs, and the selenium atom has one lone pair.

Steps

Here’s how you can easily draw the SeS₂ Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms
#4 Minimize formal charges by converting lone pairs of the atoms, and try to get a stable Lewis structure
#5 Repeat step 4 again if needed, until all charges are minimized

Now, let’s take a closer look at each step mentioned above.

#1 Draw a rough skeleton structure

• First, determine the total number of valence electrons

In the periodic table, both selenium and sulfur lie in group 16.

Hence, both selenium and sulfur have six valence electrons.

Since SeS₂ has one selenium atom and two sulfur atoms, so…

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

And the total valence electrons = 6 + 12 = 18

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

• Second, find the total electron pairs

We have a total of 18 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 = 18 ÷ 2 = 9

• Third, determine the central atom

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

Since selenium is less electronegative than sulfur, assume that the central atom is selenium.

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

• And finally, draw the rough sketch

#2 Mention lone pairs on the atoms

Here, we have a total of 9 electron pairs. And two Se — S bonds are already marked. So we have to only mark the remaining seven electron pairs as lone pairs on the sketch.

Also remember that selenium is a period 4 element, so it can keep more than 8 electrons in its last shell. And sulfur is a period 3 element, so it can also 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 selenium, there is one lone pair.

Mark the lone pairs on the sketch as follows:

#3 If needed, mention formal charges on the atoms

Use the following formula to calculate the formal charges on atoms:

Formal charge = valence electrons – nonbonding electrons – ½ bonding electrons

For selenium atom, formal charge = 6 – 2 – ½ (4) = +2

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

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

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

#4 Minimize formal charges by converting lone pairs of the atoms

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

#5 Since there are charges on atoms, repeat step 4 again

Since there are charges on selenium and sulfur atoms, again convert a lone pair of the sulfur atom to make a new Se — S bond with the selenium atom as follows:

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

Also, the above structure is more stable than the previous structures. Therefore, this structure is the stable Lewis structure of SeS₂.

Next: SeF2 Lewis structure

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