Is the molecule XeF2 polar or nonpolar? The electronegativity of Xe is 2.6
The correct Answer and Explanation is:
Answer: XeF₂ (xenon difluoride) is a nonpolar molecule.
Explanation
To determine whether XeF₂ is polar or nonpolar, we need to examine both its molecular geometry and the electronegativity differences between the atoms.
1. Electronegativity Consideration:
- Xenon (Xe): 2.6
- Fluorine (F): 4.0
- Difference in electronegativity between Xe and F = 4.0 – 2.6 = 1.4
This suggests that the Xe–F bonds are polar, as fluorine is significantly more electronegative and will pull electron density toward itself. However, the polarity of individual bonds does not automatically mean the molecule is polar.
2. Molecular Geometry:
XeF₂ has five electron domains around the xenon atom (two bonding pairs for the fluorines and three lone pairs). According to VSEPR theory, this results in a trigonal bipyramidal electron geometry. The three lone pairs occupy the equatorial positions to minimize repulsion, and the two fluorine atoms occupy the axial positions, 180° apart.
This gives XeF₂ a linear molecular shape.
3. Net Dipole Moment:
Even though each Xe–F bond is polar, the linear geometry causes the two bond dipoles to point in exactly opposite directions. As a result, these dipoles cancel each other out, and there is no net dipole moment in the molecule.
4. Conclusion:
Despite having polar bonds, the symmetrical linear shape of XeF₂ ensures that the molecule is nonpolar overall. This is a classic example where geometry plays a crucial role in molecular polarity. The cancellation of equal and opposite dipole moments makes XeF₂ a nonpolar molecule, which affects its physical properties such as solubility and boiling point.
