What is the molecular geometry of BrF_5?

• A. Octahedral
• B. Trigonal bipyramidal
• C. Tetrahedral
• D. Square pyramidal

Answer: (D)

Verified step by step guidance

1. Step 1: Determine the Lewis structure of BrF_5 by counting the total valence electrons. Bromine (Br) has 7 valence electrons, and each fluorine (F) has 7 valence electrons. So, total valence electrons = 7 (Br) + 5 × 7 (F) = 42 electrons.
2. Step 2: Draw the skeletal structure with Br as the central atom bonded to five F atoms. Use 2 electrons (one bond) for each Br–F bond, accounting for 10 electrons, and distribute the remaining electrons to complete the octets of the fluorine atoms first.
3. Step 3: After placing electrons around fluorines, assign any leftover electrons to the central bromine atom as lone pairs. In BrF_5, bromine will have one lone pair remaining after bonding with five fluorines.
4. Step 4: Use the VSEPR theory to predict the molecular geometry. Bromine has 6 regions of electron density (5 bonding pairs + 1 lone pair), which corresponds to an octahedral electron geometry.
5. Step 5: Since one position is occupied by a lone pair, the molecular geometry is derived by removing the lone pair from the octahedral shape, resulting in a square pyramidal molecular geometry.