Which of the following statements correctly describes the Lewis dot structure of the KrF_4 molecule?

• A. Krypton (Kr) is surrounded by four fluorine (F) atoms, each forming a single bond, and there are two lone pairs on Kr.
• B. Krypton (Kr) forms double bonds with each fluorine (F) atom, with no lone pairs on Kr.
• C. Krypton (Kr) is surrounded by four fluorine (F) atoms, each forming a single bond, and there are no lone pairs on Kr.
• D. Krypton (Kr) forms single bonds with two fluorine (F) atoms and double bonds with the other two, with one lone pair on Kr.

Answer: (A)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons available for bonding. Krypton (Kr) is a noble gas with 8 valence electrons, and each fluorine (F) atom has 7 valence electrons. Since there are 4 fluorine atoms, total valence electrons = 8 (Kr) + 4 × 7 (F) = 8 + 28 = 36 electrons.
2. Step 2: Draw a skeletal structure with Kr as the central atom bonded to four fluorine atoms. Each Kr–F bond is initially considered a single bond, which accounts for 4 bonds × 2 electrons = 8 electrons.
3. Step 3: Distribute the remaining electrons to satisfy the octet rule for the fluorine atoms first. Each fluorine needs 6 more electrons (3 lone pairs) to complete its octet, so 4 fluorines × 6 electrons = 24 electrons are assigned as lone pairs on fluorines.
4. Step 4: After assigning electrons to fluorines and bonding pairs, calculate the remaining electrons to place on the central krypton atom. Total electrons used so far are 8 (bonds) + 24 (fluorine lone pairs) = 32 electrons, so 36 - 32 = 4 electrons remain, which form 2 lone pairs on Kr.
5. Step 5: Confirm the structure by checking the octet rule and formal charges. Krypton has 4 bonding pairs and 2 lone pairs, completing its expanded octet (which is allowed for elements in period 4 and beyond), and each fluorine has a full octet with single bonds to Kr.