CBr4 Lewis structure

CBr₄ (carbon tetrabromide) has one carbon atom and four bromine atoms.

In the CBr₄ Lewis structure, there are four single bonds around the carbon atom, with four bromine atoms attached to it, and on each bromine atom, there are three lone pairs.

Alternative method: Lewis structure of CBr₄

Rough sketch

• First, determine the total number of valence electrons

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

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

Since CBr₄ has one carbon atom and four bromine atoms, so…

Valence electrons of one carbon 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: Carbon 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 carbon is less electronegative than bromine, assume that the central atom is carbon.

Therefore, place carbon 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 C — 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 carbon is a period 2 element, so it can not 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 carbon, 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 carbon atom, formal charge = 4 – 0 – ½ (8) = 0

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

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

Final structure

The final structure of CBr₄ includes a central carbon atom linked to four bromine atoms through single covalent bonds. In this configuration, the carbon atom satisfies the octet rule by forming four total bonds, while each bromine atom fulfills its octet by maintaining three lone pairs alongside its single shared bond. Within this layout, all five atoms achieve a stable electronic state through these four shared pairs. This arrangement 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 carbon tetrabromide.

Next: OCN^– Lewis structure

External video

• CBr4 Lewis Structure: How to Draw the Lewis Structure for CBr4 – YouTube • Wayne Breslyn

External links

• https://www.thegeoexchange.org/chemistry/bonding/Lewis-Structures/CBr4-lewis-structure.html
• https://topblogtenz.com/cbr4-lewis-structure-molecular-geometry-polarity/
• https://lambdageeks.com/cbr4-lewis-structure/
• https://sciedutut.com/how-to-draw-a-cbr4-lewis-structure/