Which of the following molecules is nonpolar? PCl; XeF4; H2O
The Correct Answer and Explanation is:
Correct Answer: XeF₄ is nonpolar.
Explanation:
To determine the polarity of a molecule, both its molecular geometry and the electronegativity difference between the atoms must be considered. A molecule is nonpolar if the dipole moments of its bonds cancel out due to a symmetrical shape.
1. PCl (Phosphorus Monochloride):
This molecule appears to be phosphorus monochloride, but the correct molecular formula might be ambiguous. If assumed to be PCl₃, the molecule has a trigonal pyramidal shape due to a lone pair on phosphorus. The P–Cl bonds are polar because chlorine is more electronegative than phosphorus. The asymmetrical geometry leads to a net dipole moment, making the molecule polar.
2. XeF₄ (Xenon Tetrafluoride):
XeF₄ has a central xenon atom bonded to four fluorine atoms, with two lone pairs on xenon. The electron geometry is octahedral, and the molecular shape is square planar. The fluorine atoms are arranged symmetrically around the xenon, and the lone pairs are positioned opposite each other. Although each Xe–F bond is polar (fluorine is highly electronegative), the symmetrical arrangement of these bonds causes the dipoles to cancel out. Therefore, XeF₄ is nonpolar.
3. H₂O (Water):
Water has a bent molecular shape due to the two lone pairs on the oxygen atom. The O–H bonds are polar because of the electronegativity difference between oxygen and hydrogen. The bent shape means the bond dipoles do not cancel each other. As a result, water has a strong net dipole moment, making it polar.
Conclusion:
Among the given molecules, XeF₄ is the only one that is nonpolar due to its symmetrical square planar shape, which causes bond dipoles to cancel out.
