Which of the following best describes the electron domain geometry and molecular geometry of the BrCl4− ion based on its Lewis structure?

• A. Electron domain geometry: octahedral; Molecular geometry: square planar
• B. Electron domain geometry: trigonal bipyramidal; Molecular geometry: seesaw
• C. Electron domain geometry: octahedral; Molecular geometry: tetrahedral
• D. Electron domain geometry: tetrahedral; Molecular geometry: tetrahedral

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons for the BrCl4⁻ ion. Bromine (Br) has 7 valence electrons, each chlorine (Cl) has 7 valence electrons, and the negative charge adds 1 extra electron. Calculate the sum: \$7 + 4 \times 7 + 1$.
2. Step 2: Draw the Lewis structure by placing Br as the central atom bonded to four Cl atoms. Distribute the remaining electrons to satisfy the octet rule for each atom, placing lone pairs as needed.
3. Step 3: Count the electron domains (regions of electron density) around the central Br atom. These include bonding pairs and lone pairs. For BrCl4⁻, identify how many bonding pairs and lone pairs are present.
4. Step 4: Use the VSEPR theory to determine the electron domain geometry based on the total number of electron domains. For example, 6 electron domains correspond to an octahedral electron domain geometry.
5. Step 5: Determine the molecular geometry by considering only the positions of atoms (bonding pairs) and ignoring lone pairs. For BrCl4⁻, with 2 lone pairs and 4 bonding pairs in an octahedral arrangement, the molecular geometry is square planar.