Which of the following statements correctly describes the Lewis dot structure of the Br\(_3^-\) ion?

• A. It consists of three bromine atoms in a linear arrangement, with two single bonds and three lone pairs on each terminal Br atom, and two lone pairs on the central Br atom.
• B. It consists of three bromine atoms in a linear arrangement, with double bonds between each pair of bromine atoms.
• C. It consists of three bromine atoms in a triangular arrangement, with each atom sharing one electron pair with the others.
• D. It consists of three bromine atoms in a bent arrangement, with one single bond and one double bond.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons for the Br\(_3^-\) ion. Each bromine atom has 7 valence electrons, and the negative charge adds 1 extra electron. So, total valence electrons = 3 \times 7 + 1.
2. Step 2: Arrange the three bromine atoms in a linear fashion because halogen polyatomic ions like Br\(_3^-\) typically adopt a linear geometry due to electron repulsion and bonding preferences.
3. Step 3: Connect the bromine atoms with single bonds initially. Each single bond represents 2 electrons shared between atoms. Subtract these bonding electrons from the total valence electrons to find how many remain for lone pairs.
4. Step 4: Distribute the remaining electrons as lone pairs around the bromine atoms to satisfy the octet rule. Terminal bromines will have three lone pairs each, and the central bromine will have two lone pairs, accounting for the extra electron from the negative charge.
5. Step 5: Confirm the formal charges on each bromine atom to ensure the most stable Lewis structure. The central bromine typically carries the negative charge, consistent with the extra lone pair, and the structure is linear with two single bonds.