Draw and Explain the Lewis Structure for the BBr3 Molecule, Which Is an Exception to the Octet Rule

The Lewis structure for boryl bromide (BBr3) illustrates an important exception to the octet rule. In this molecule, boron (B) is the central atom, surrounded by three bromine (Br) atoms.

To draw the Lewis structure, follow these steps:

  1. Count the total valence electrons: Boron has 3 valence electrons, and each bromine has 7, leading to a total of 3 + (3 × 7) = 24 valence electrons.
  2. Place the boron atom in the center, then attach each bromine atom to the boron with a single bond. This accounts for 6 valence electrons (2 electrons for each of the 3 B-Br bonds).
  3. Distribute the remaining valence electrons to the bromine atoms to satisfy their octet. Each bromine will need 6 additional electrons (3 lone pairs) to complete its octet. This uses up the remaining 18 electrons.

Now, let’s depict the structure:

      Br
      |
   Br-Br
      |
      Br

In this structure, boron only has 6 electrons around it (3 bonds with bromine), which is less than an octet. This situation is an exception to the octet rule, as boron has a tendency to be electron-deficient and can form stable compounds with fewer than 8 electrons. The ability of boron to form these compounds is related to its unique electron configuration and small size, enabling it to accommodate fewer electrons around it without resulting in instability.

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