# SiF5- Lewis structure

SiF5 has one silicon atom and five fluorine atoms.

In SiF5 Lewis structure, there are five single bonds around the silicon atom, with five fluorine atoms attached to it, and on each fluorine atom, there are three lone pairs.

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

Contents

## Steps

To properly draw the SiF5 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, silicon lies in group 14, and fluorine lies in group 17.

Hence, silicon has four valence electrons and fluorine has seven valence electrons.

Since SiF5 has one silicon atom and five fluorine atoms, so…

Valence electrons of one silicon atom = 4 × 1 = 4
Valence electrons of five fluorine atoms = 7 × 5 = 35

Now the SiF5 has a negative (-1) charge, so we have to add one more electron.

So the total valence electrons = 4 + 35 + 1 = 40

• Second, find the total electron pairs

We have a total of 40 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 = 40 ÷ 2 = 20

• Third, determine the central atom

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

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

Therefore, place silicon 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 20 electron pairs. And five Si — F bonds are already marked. So we have to only mark the remaining fifteen electron pairs as lone pairs on the sketch.

Also remember that silicon is a period 3 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 silicon, there is zero lone pair because all fifteen electron pairs are over.

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 silicon atom, formal charge = 4 – 0 – ½ (10) = -1

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

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

In the above structure, you can see that the central atom (silicon) 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 SiF5.

And since the SiF5 has a negative (-1) charge, mention that charge on the Lewis structure by drawing brackets as follows: