What is the molecular geometry of BrF_5?

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

Answer: (B)

Verified step by step guidance

1. Step 1: Determine the Lewis structure of BrF_5. Bromine (Br) is the central atom bonded to five fluorine (F) atoms. Count the total valence electrons: Br has 7, each F has 7, so total electrons = 7 + 5×7 = 42 electrons.
2. Step 2: Draw single bonds between Br and each F atom, using 10 electrons (5 bonds × 2 electrons each). Distribute the remaining electrons to complete the octets of the fluorine atoms first.
3. Step 3: After completing the fluorine octets, place any remaining electrons on the central bromine atom. Bromine will have one lone pair of electrons because it can expand its octet.
4. Step 4: Use VSEPR theory to determine the molecular geometry. With 5 bonding pairs and 1 lone pair around bromine, the electron pair geometry is octahedral, but the molecular shape is affected by the lone pair.
5. Step 5: Recognize that the presence of one lone pair in an octahedral electron geometry results in a square pyramidal molecular geometry for BrF_5.