# SiBr4 Lewis structure

SiBr4 (silicon tetrabromide) has one silicon atom and four bromine atoms.

In the SiBr4 Lewis structure, there are four single bonds around the silicon atom, with four bromine atoms attached to it, and on each bromine atom, there are three lone pairs.

Contents

## Steps

Here’s how you can easily draw the SiBr4 Lewis structure step by step:

#1 Draw a rough skeleton structure
#2 Mention lone pairs on the atoms
#3 If needed, mention formal charges on the atoms

Now, let’s take a closer look at each step mentioned above.

### #1 Draw a rough skeleton structure

• First, determine the total number of valence electrons

In the periodic table, silicon lies in group 14, and bromine lies in group 17.

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

Since SiBr4 has one silicon atom and four bromine atoms, so…

Valence electrons of one silicon atom = 4 × 1 = 4
Valence electrons of four bromine atoms = 7 × 4 = 28

And the total valence electrons = 4 + 28 = 32

• Second, find the total electron pairs

We have a total of 32 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 = 32 ÷ 2 = 16

• Third, determine the central atom

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

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

Therefore, place silicon in the center and bromines on either side.

• And finally, draw the rough sketch

### #2 Mention lone pairs on the atoms

Here, we have a total of 16 electron pairs. And four Si — Br bonds are already marked. So we have to only mark the remaining twelve 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 bromine is a period 4 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 bromines.

So for each bromine, there are three lone pairs, and for silicon, there is zero lone pair because all twelve electron pairs are over.

Mark the lone pairs on the sketch as follows:

### #3 If needed, mention formal charges on the atoms

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 (8) = 0

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

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

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

Therefore, this structure is the stable Lewis structure of SiBr4.