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.

Alternative method: Lewis structure of SiBr₄

Rough sketch

• 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

Learn how to find: Silicon valence electrons and Bromine valence electrons

• 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

Lone pair

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:

Formal charge

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.

Final structure

The final structure of SiBr₄ comprises a central silicon atom linked to four bromine atoms through single covalent bonds. In this arrangement, the silicon atom satisfies the octet rule by forming four total bonds, while each bromine atom also fulfills its octet by retaining three lone pairs alongside its single shared bond. Within this layout, every atom achieves a complete valence shell without the need for an expanded octet or multiple bonds. This configuration represents the most stable state for the molecule because it results in a formal charge of zero for every atom involved. Accordingly, this specific electronic distribution serves as the definitive and most accurate Lewis representation of silicon tetrabromide.

Next: XeOF₄ Lewis structure

External video

• SiBr4 Lewis Structure: How to Draw the Lewis Structure for SiBr4 (Silicon Tetrabromide) – YouTube • Wayne Breslyn

External links

• https://techiescientist.com/sibr4-lewis-structure/
• https://oneclass.com/homework-help/chemistry/7030380-sibr4-lewis-structure.en.html