# SeCl4 Lewis structure

SeCl4 (selenium tetrachloride) has one selenium atom and four chlorine atoms.

In the SeCl4 Lewis structure, there are four single bonds around the selenium atom, with four chlorine atoms attached to it. Each chlorine atom has three lone pairs, and the selenium atom has one lone pair.

Contents

## Steps

To properly draw the SeCl4 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, selenium lies in group 16, and chlorine lies in group 17.

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

Since SeCl4 has one selenium atom and four chlorine atoms, so…

Valence electrons of one selenium atom = 6 × 1 = 6
Valence electrons of four chlorine atoms = 7 × 4 = 28

And the total valence electrons = 6 + 28 = 34

• Second, find the total electron pairs

We have a total of 34 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 = 34 ÷ 2 = 17

• 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

### #2 Next, indicate lone pairs on the atoms

Here, we have a total of 17 electron pairs. And four Se — Cl bonds are already marked. So we have to only mark the remaining thirteen 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 is one lone pair.

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 selenium atom, formal charge = 6 – 2 – ½ (8) = 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 SeCl4.