Lewis structure of SeCl4

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Lewis structure of SeCl4
Lewis structure of SeCl4 | Image: Root Memory

The Lewis structure of SeCl4 contains four single bonds, with selenium in the center, and four chlorines on either side. There are three lone pairs on each chlorine atom, and one lone pair on the selenium atom.

Steps

By using the following steps, you can easily draw the Lewis structure of SeCl4.

#1 Draw skeleton
#2 Show chemical bond
#3 Mark lone pairs
#4 Calculate formal charge and check stability (if octet is already completed on central atom)

Let’s one by one discuss each step in detail.

#1 Draw skeleton

In this step, first calculate the total number of valence electrons. And then, decide the central atom.

  • Let’s calculate the total number of valence electrons

We know that… selenium is a group 16 element and chlorine is a group 17 element. Hence, selenium has six valence electrons and chlorine has seven valence electrons.

Now SeCl4 has one selenium atom and four chlorine atoms.

So the total number of valence electrons = valence electrons of selenium atom + (valence electrons of chlorine atom × 4)

Therefore, the total number of valence electrons = 6 + 28 = 34

  • Now decide the central atom

The atom with the least electronegative value is placed at the center. By looking at the periodic table, we get the electronegativity values for selenium and chlorine as follows:

Electronegativity value of selenium = 2.55
Electronegativity value of chlorine = 3.16

Obviously, selenium is less electronegative than chlorine. Hence, assume that selenium is the central atom.

So now, put selenium in the center and chlorines on either side. And draw the rough skeleton structure for the Lewis structure of SeCl4 something like this:

Skeleton structure for Lewis structure of SeCl4 | Image: Root Memory

#2 Show chemical bond

Place two electrons between the atoms to show a chemical bond. Since selenium is surrounded by four chlorines, use eight electrons to show four chemical bonds as follows:

Four chemical bonds shown between atoms | Image: Root Memory

#3 Mark lone pairs

As calculated earlier, we have a total of 34 valence electrons. And in the above structure, we have already used eight valence electrons. Hence, twenty-six valence electrons are remaining.

Two valence electrons represent one lone pair. So twenty-six valence electrons = thirteen lone pairs.

Note that selenium is a period 4 element, so it can 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.

Also, make sure that you start marking these lone pairs on outside atoms first. And then, on the central atom.

The outside atoms are chlorines, so each chlorine will get three lone pairs. And the central atom (selenium) will get one lone pair.

So the Lewis structure of SeCl4 looks something like this:

Lone pairs marked on Lewis structure of SeCl4 | Image: Root Memory

In the above structure, you can see that the octet is completed on the central atom (selenium), and also on the outside atoms. Therefore, the octet rule is satisfied.

After completing the octet, one last thing we need to do is, calculate the formal charge and check the stability of the above structure.

#4 Calculate formal charge and check stability

The following formula is used to calculate the formal charges on atoms:

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

Collect the data from the above structure and then, write it down below as follows:

  • For selenium atom

Valence electrons = 6
Nonbonding electrons = 2
Bonding electrons = 8

Formal charge = 6 – 2 – ½ (8) = 0

  • For each chlorine atom

Valence electrons = 7
Nonbonding electrons = 6
Bonding electrons = 2

Formal charge = 7 – 6 – ½ (2) = 0

Mention the formal charges of atoms on the structure. So the Lewis structure of SeCl4 looks something like this:

Formal charges are calculated, and got the stable Lewis structure of SeCl4 | Image: Root Memory

In the above structure, you can see that the formal charges of both (selenium and chlorine) are zero. Therefore, this is the stable Lewis structure of SeCl4.

And each horizontal line drawn in the above structure represents a pair of bonding valence electrons.

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Deep

Rootmemory.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.

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