Which of the following best represents the Lewis dot structure for phosphorus trichloride (PCl_3)?

• A. A central P atom with three single bonds to Cl atoms and one lone pair on P.
• B. A central P atom with three double bonds to Cl atoms and no lone pairs on P.
• C. A central P atom with three single bonds to Cl atoms and no lone pairs on P.
• D. A central P atom with three single bonds to Cl atoms and one lone pair on each Cl atom.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons for phosphorus trichloride (PCl_3). Phosphorus (P) is in group 15 and has 5 valence electrons, and each chlorine (Cl) atom is in group 17 with 7 valence electrons. Since there are three Cl atoms, calculate the total valence electrons as \$5 + 3 \times 7$.
2. Step 2: Identify the central atom, which is usually the least electronegative element. In PCl_3, phosphorus is the central atom, and the three chlorine atoms will be bonded to it.
3. Step 3: Draw single bonds between the central phosphorus atom and each chlorine atom. Each single bond represents 2 electrons shared between atoms.
4. Step 4: Distribute the remaining valence electrons to satisfy the octet rule for the chlorine atoms first, placing lone pairs around each Cl to complete their octets.
5. Step 5: Place any leftover electrons on the central phosphorus atom as lone pairs. Since phosphorus can have an expanded octet, check if placing one lone pair on P satisfies the total valence electron count and the octet rule for all atoms.