To determine which molecule is more polar between SF4 and CF4, we need to consider their molecular geometry and electronegativity differences.
SF4 (sulfur tetrafluoride) has a see-saw molecular shape due to the presence of one lone pair of electrons on the sulfur atom. This uneven distribution of charge leads to a dipole moment because the bonds between sulfur and fluorine are polar, with fluorine being more electronegative than sulfur. As a result, the molecular shape does not allow the dipoles to cancel out entirely, making SF4 a polar molecule.
On the other hand, CF4 (carbon tetrafluoride) has a tetrahedral shape with no lone pairs on the central carbon atom. All the C-F bonds are polar because fluorine is more electronegative than carbon; however, due to the symmetrical tetrahedral geometry, the bond dipoles cancel each other out. Hence, CF4 is a nonpolar molecule.
In conclusion, SF4 is more polar than CF4 because its molecular geometry allows for a net dipole moment, while CF4‘s symmetrical shape results in a cancellation of dipoles.