Draw the Lewis structure of KrF2 molecule. What is the polarity of this molecule and the hybridization on the central atom, krypton, respectively?
The Correct Answer and Explanation is:
Correct Answer:
- Polarity: Nonpolar
- Hybridization of central atom (Krypton): sp³d
Explanation
The molecule KrF₂ (krypton difluoride) consists of one krypton (Kr) atom bonded to two fluorine (F) atoms. To determine the Lewis structure, start by calculating the total number of valence electrons. Krypton is a noble gas in group 18 with 8 valence electrons, and each fluorine atom (group 17) has 7 valence electrons. Therefore, KrF₂ has:
Total valence electrons = 8 (Kr) + 2 × 7 (F) = 22 electrons
In the Lewis structure, krypton is the central atom. Place one single bond between Kr and each F atom, using 2 electrons per bond (4 electrons total). Each F atom then completes its octet with 6 more electrons (3 lone pairs), using 12 electrons total. That leaves 6 electrons (22 – 4 – 12 = 6), which are placed as 3 lone pairs on krypton.
Thus, the Lewis structure of KrF₂ shows:
- Two bonding pairs (Kr–F)
- Three lone pairs on Kr
This gives a total of five electron domains around krypton. According to VSEPR theory, five electron domains correspond to trigonal bipyramidal electron geometry. To minimize electron pair repulsion, the lone pairs occupy the equatorial positions, and the fluorine atoms occupy the axial positions. This results in a linear molecular shape.
Because the two fluorine atoms are identical and symmetrically placed around the central atom in a linear geometry, their dipoles cancel out. Therefore, KrF₂ is a nonpolar molecule, despite having highly electronegative fluorine atoms.
To accommodate five electron regions, the central atom (Kr) undergoes sp³d hybridization—one s orbital, three p orbitals, and one d orbital mix to form five hybrid orbitals.
In summary:
- Lewis structure: Kr with two F atoms and three lone pairs
- Molecular shape: Linear
- Polarity: Nonpolar
- Hybridization: sp³d
