Final answer:
CH3F and SF4 are polar molecules because they have asymmetric geometries with an uneven distribution of electron density. XeF2 is nonpolar despite having polar bonds because it has a symmetric, linear shape that causes the dipoles to cancel. BrF5 is polar due to its square pyramidal geometry.
Step-by-step explanation:
To determine whether a molecule is polar or nonpolar, one must consider the molecule's geometry and the electronegativity of its atoms. The presence of polar bonds and the symmetry of the molecule all play a role in this.
- CH₃F (Methyl fluoride): This molecule is polar because it has an asymmetric shape (tetrahedral with three hydrogen atoms and one fluorine atom) and fluorine is more electronegative than carbon, creating a dipole moment.
- BrF₅ (Bromine pentafluoride): Despite having polar bonds, the molecular geometry is square pyramidal which is asymmetric, leading to a polar molecule.
- XeF₂ (Xenon difluoride): Even though it has polar bonds, the molecular geometry is linear with symmetric charge distribution, resulting in a nonpolar molecule as the bond dipoles cancel out.
- SF₄ (Sulfur tetrafluoride): This molecule is polar due to its see-saw shape, which is asymmetric. The lone pair on sulfur creates an uneven distribution of electron density, leading to a net dipole moment.
In summary, based on their molecular geometry and bond polarities, CH₃F and SF₄ are polar molecules, while XeF₂ is nonpolar despite containing polar bonds. BrF₅ is also polar due to its molecular geometry.