# SeF5- Lewis structure

SeF5 has one selenium atom and five fluorine atoms.

In SeF5 Lewis structure, there are five single bonds around the selenium atom, with five fluorine atoms attached to it. Each fluorine atom has three lone pairs, and the selenium atom has one lone pair.

Also, there is a negative (-1) charge on the selenium atom.

Contents

## Steps

To properly draw the SeF5 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 fluorine lies in group 17.

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

Since SeF5 has one selenium atom and five fluorine atoms, so…

Valence electrons of one selenium atom = 6 × 1 = 6
Valence electrons of five fluorine atoms = 7 × 5 = 35

Now the SeF5 has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 6 + 35 + 1 = 42

• Second, find the total electron pairs

We have a total of 42 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 = 42 ÷ 2 = 21

• Third, determine the central atom

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

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

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

• And finally, draw the rough sketch

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

Here, we have a total of 21 electron pairs. And five Se — F bonds are already marked. So we have to only mark the remaining sixteen 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 fluorine is a period 2 element, so it can not keep more than 8 electrons in its last shell.

Always start to mark the lone pairs from outside atoms. Here, the outside atoms are fluorines.

So for each fluorine, 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 (10) = -1

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

Here, the selenium atom has a charge, so mark it on the sketch as follows:

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

Therefore, this structure is the most stable Lewis structure of SeF5.

And since the SeF5 has a negative (-1) charge, mention that charge on the Lewis structure by drawing brackets as follows: