Which of the following statements correctly describes the Lewis dot structure of a neutral molecule of ArF_2?

• A. Argon is the central atom, bonded to two fluorine atoms, with no lone pairs on argon.
• B. Argon is the central atom, bonded to two fluorine atoms, with one lone pair on argon.
• C. Fluorine is the central atom, bonded to two argon atoms, with two lone pairs on fluorine.
• D. Argon is the central atom, bonded to two fluorine atoms, with three lone pairs on argon.

Answer: (D)

Verified step by step guidance

1. Step 1: Identify the central atom in the molecule ArF_2. Typically, the least electronegative atom (excluding hydrogen) is the central atom. Argon (Ar) is a noble gas and less electronegative than fluorine (F), so Ar is the central atom.
2. Step 2: Determine the total number of valence electrons available. Argon has 8 valence electrons, and each fluorine has 7 valence electrons. For ArF_2, total valence electrons = 8 (Ar) + 2 × 7 (F) = 22 electrons.
3. Step 3: Draw single bonds between the central atom (Ar) and each fluorine atom. Each bond uses 2 electrons, so 2 bonds use 4 electrons. Subtract these from the total valence electrons to find remaining electrons: 22 - 4 = 18 electrons left.
4. Step 4: Distribute the remaining electrons as lone pairs to satisfy the octet rule for the fluorine atoms first. Each fluorine needs 6 more electrons (3 lone pairs) to complete its octet, so 2 fluorines require 12 electrons. Subtract these from the remaining electrons: 18 - 12 = 6 electrons left.
5. Step 5: Assign the remaining 6 electrons as lone pairs on the central argon atom. Since each lone pair consists of 2 electrons, 6 electrons correspond to 3 lone pairs on argon. This completes the Lewis structure with argon bonded to two fluorines and three lone pairs on argon.