What is the molecular geometry of NF_3?

• A. Tetrahedral
• B. Trigonal pyramidal
• C. Bent
• D. Trigonal planar

Answer: (B)

Verified step by step guidance

1. Step 1: Determine the Lewis structure of NF_3 by counting the total valence electrons. Nitrogen has 5 valence electrons, and each fluorine has 7 valence electrons, so total valence electrons = 5 + 3 \times 7 = 26 electrons.
2. Step 2: Draw the nitrogen atom in the center bonded to three fluorine atoms with single bonds. Each bond accounts for 2 electrons, so 3 bonds use 6 electrons, leaving 20 electrons to be placed as lone pairs.
3. Step 3: Complete the octets of the fluorine atoms by placing 6 electrons (3 lone pairs) around each fluorine. This uses 18 electrons (3 fluorines \times 6 electrons each).
4. Step 4: Place the remaining 2 electrons as a lone pair on the nitrogen atom. Now nitrogen has 3 bonding pairs and 1 lone pair.
5. Step 5: Use VSEPR theory to determine the molecular geometry. With 3 bonding pairs and 1 lone pair, the electron geometry is tetrahedral, but the molecular shape (ignoring the lone pair) is trigonal pyramidal.