After drawing the Lewis structure of PF3, what are its electron domain geometry and molecular geometry?

• A. Electron domain geometry: trigonal bipyramidal; Molecular geometry: T-shaped
• B. Electron domain geometry: trigonal planar; Molecular geometry: trigonal planar
• C. Electron domain geometry: tetrahedral; Molecular geometry: trigonal pyramidal
• D. Electron domain geometry: tetrahedral; Molecular geometry: tetrahedral

Answer: (C)

Verified step by step guidance

1. Step 1: Draw the Lewis structure of PF3 by first 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 × 7) = 26 electrons.
2. Step 2: Connect the phosphorus atom to each fluorine atom with a single bond. Each bond uses 2 electrons, so 3 bonds use 6 electrons. Distribute the remaining electrons to complete the octets of the fluorine atoms first.
3. Step 3: After placing lone pairs on fluorines, assign any leftover electrons to the phosphorus atom. Check if phosphorus has a complete octet or if it has lone pairs. In PF3, phosphorus has one lone pair and three bonding pairs.
4. Step 4: Determine the electron domain geometry by counting all electron domains (bonding pairs + lone pairs) around phosphorus. Here, there are 4 electron domains (3 bonding pairs + 1 lone pair), which corresponds to a tetrahedral electron domain geometry.
5. Step 5: Determine the molecular geometry by considering only the positions of atoms (ignoring lone pairs). With one lone pair and three bonded atoms, the molecular geometry is trigonal pyramidal.