Which of the following statements correctly describes the Lewis dot structure of the ion Br3−?

• A. Br3− has a trigonal planar structure with three single bonds.
• B. Br3− has a linear structure with two single bonds and one lone pair on the central Br atom.
• C. Br3− has a linear structure with three Br atoms sharing a single pair of electrons.
• D. Br3− has a bent structure with one double bond and one single bond.

Answer: (B)

Verified step by step guidance

1. Step 1: Identify the central atom and the total number of valence electrons. For Br3−, bromine (Br) atoms each have 7 valence electrons, and the ion has an extra electron due to the negative charge, so total valence electrons = 3 × 7 + 1 = 22 electrons.
2. Step 2: Arrange the three bromine atoms in a linear fashion because halogen polyatomic ions like Br3− typically have a linear geometry due to electron repulsion and bonding preferences.
3. Step 3: Draw single bonds between the central bromine atom and each terminal bromine atom. Each single bond accounts for 2 electrons, so 4 electrons are used in bonding.
4. Step 4: Distribute the remaining electrons as lone pairs to satisfy the octet rule for each bromine atom. The central bromine will have lone pairs remaining after bonding, which influences the molecular shape.
5. Step 5: Determine the molecular geometry by considering the number of bonding pairs and lone pairs on the central atom. With two bonding pairs and one lone pair, the shape is linear, consistent with the correct description of Br3−.