What is the molecular geometry of PF3?

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

Answer: (D)

Verified step by step guidance

1. Determine the Lewis structure of PF3 by counting the total valence electrons: Phosphorus (P) has 5 valence electrons, and each Fluorine (F) has 7 valence electrons. Since there are 3 fluorines, total valence electrons = 5 + 3 \times 7 = 26 electrons.
2. Draw the Lewis structure with phosphorus as the central atom bonded to three fluorine atoms. Use single bonds between P and each F, which accounts for 6 electrons (3 bonds \times 2 electrons each).
3. Distribute the remaining electrons to complete the octets of the fluorine atoms first, then place any leftover electrons on the phosphorus atom as lone pairs. After filling fluorine octets, place the remaining electrons as a lone pair on phosphorus.
4. Count the regions of electron density (bonding and lone pairs) around the central phosphorus atom. There are 3 bonding pairs (P-F bonds) and 1 lone pair, making a total of 4 regions of electron density.
5. Use VSEPR theory to determine the molecular geometry: 4 regions of electron density with 1 lone pair corresponds to a trigonal pyramidal shape, because the lone pair repels the bonding pairs, distorting the shape from tetrahedral to trigonal pyramidal.