CH2Br2 Lewis structure

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CH₂Br₂ (dibromomethane) has one carbon atom, two hydrogen atoms, and two bromine atoms.

In the CH₂Br₂ Lewis structure, there are four single bonds around the carbon atom, with two hydrogen atoms and two bromine atoms attached to it, and on each bromine atom, there are three lone pairs.

Steps

Here’s how you can easily draw the CH₂Br₂ 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, carbon lies in group 14, hydrogen lies in group 1, and bromine lies in group 17.

Hence, carbon has four valence electrons, hydrogen has one valence electron, and bromine has seven valence electrons.

Since CH₂Br₂ has one carbon atom, two hydrogen atoms, and two bromine atoms, so…

Valence electrons of one carbon atom = 4 × 1 = 4
Valence electrons of two hydrogen atoms = 1 × 2 = 2
Valence electrons of two bromine atoms = 7 × 2 = 14

And the total valence electrons = 4 + 2 + 14 = 20

Learn how to find: Carbon valence electrons, Hydrogen valence electrons, and Bromine valence electrons

• Second, find the total electron pairs

We have a total of 20 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 = 20 ÷ 2 = 10

• Third, determine the central atom

Here hydrogen can not be the central atom. Because the central atom is bonded with at least two other atoms, and hydrogen has only one electron in its last shell, so it can not make more than one bond.

Now we have to choose the central atom from carbon and bromine. 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 hydrogen and bromine on either side.

• And finally, draw the rough sketch

#2 Mention lone pairs on the atoms

Here, we have a total of 10 electron pairs. And four bonds are already marked. So we have to only mark the remaining six 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. Hydrogen is a period 1 element, so it can not keep more than 2 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 hydrogens and bromines. But no need to mark on hydrogen, because each hydrogen has already two electrons.

So for each bromine, there are three lone pairs, and for carbon, there is zero lone pair because all six 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 carbon atom, formal charge = 4 – 0 – ½ (8) = 0

For each hydrogen atom, formal charge = 1 – 0 – ½ (2) = 0

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

Here, the atoms do not have charges, so no need to mark the charges.

In the above structure, you can see that the central atom (carbon) forms an octet. The outside atoms (bromines) also form an octet, and both hydrogens form a duet. Hence, the octet rule and duet rule are satisfied.

Therefore, this structure is the stable Lewis structure of CH₂Br₂.

Next: C₂F₂ Lewis structure

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External links

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