SeCl2 Lewis structure

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SeCl2 Lewis Structure
SeCl2 Lewis structure

SeCl2 (selenium dichloride) has one selenium atom and two chlorine atoms.

In SeCl2 Lewis structure, there are two single bonds around the selenium atom, with two chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the selenium atom has two lone pairs.


Use these steps to correctly draw the SeCl2 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

Let’s discuss each step in more detail.

#1 First draw a rough sketch

  • First, determine the total number of valence electrons
Periodic table

In the periodic table, selenium lies in group 16, and chlorine lies in group 17.

Hence, selenium has six valence electrons and chlorine has seven valence electrons.

Since SeCl2 has one selenium atom and two chlorine atoms, so…

Valence electrons of one selenium atom = 6 × 1 = 6
Valence electrons of two chlorine atoms = 7 × 2 = 14

And the total valence electrons = 6 + 14 = 20

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

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

  • And finally, draw the rough sketch
SeCl2 Lewis Structure (Step 1)
Rough sketch of SeCl2 Lewis structure

#2 Mark lone pairs on the atoms

Here, we have a total of 10 electron pairs. And two Se — 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 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.

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 selenium, there are two lone pairs.

Mark the lone pairs on the sketch as follows:

SeCl2 Lewis Structure (Step 2)
Lone pairs marked, and got the stable Lewis structure of SeCl2

#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 selenium atom, formal charge = 6 – 4 – ½ (4) = 0

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

Here, both selenium and chlorine atoms do not have charges, so no need to mark the charges.

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

Therefore, this structure is the stable Lewis structure of SeCl2.

Next: C2F4 Lewis structure

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