Which of the following statements correctly describes the Lewis dot structure of the BrCl_4^- ion?

• A. Bromine is the central atom, surrounded by four chlorine atoms, each bonded by a single bond, and there is one lone pair on bromine.
• B. Chlorine is the central atom, surrounded by four bromine atoms, each bonded by a single bond, and one lone pair on chlorine.
• C. Bromine is the central atom, surrounded by four chlorine atoms, each bonded by a double bond, and no lone pairs on bromine.
• D. Bromine is the central atom, surrounded by four chlorine atoms, each bonded by a single bond, and there are two lone pairs on bromine.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the central atom by considering electronegativity and the number of atoms. Bromine (Br) is less electronegative than chlorine (Cl), so bromine is typically the central atom in BrCl_4^-.
2. Step 2: Count the total number of valence electrons. Bromine has 7 valence electrons, each chlorine has 7, and there are 4 chlorines, so total from atoms is 7 + (4 × 7) = 35. Since the ion has a -1 charge, add 1 more electron, making a total of 36 valence electrons.
3. Step 3: Draw single bonds between the central bromine atom and each of the four chlorine atoms. Each single bond uses 2 electrons, so 4 bonds use 8 electrons.
4. Step 4: Distribute the remaining electrons to satisfy the octet rule. First, complete the octets of the chlorine atoms by adding lone pairs. Each chlorine needs 6 more electrons (3 lone pairs) to complete its octet, so 4 chlorines × 6 electrons = 24 electrons used.
5. Step 5: Assign the remaining electrons to the central bromine atom as lone pairs. After bonding and filling chlorine octets, the leftover electrons will form lone pairs on bromine. Count these lone pairs to confirm the correct number on bromine.