Final answer:
CCl₄ contains polar bonds but is nonpolar overall due to its symmetric tetrahedral shape which cancels out dipole moments. In contrast, SO₂, H₂S, NH₃, and PF₃ are polar molecules because of their non-symmetrical shapes.
Step-by-step explanation:
The molecule CCl₄ (carbon tetrachloride) contains polar bonds but is a nonpolar molecule. This is due to its tetrahedral geometry where each of the four chlorine atoms is symmetrically spaced around the central carbon atom, resulting in a cancellation of the dipole moments. While the C-Cl bonds are polar because of the difference in electronegativity between carbon and chlorine, the symmetry of the molecule ensures that it is nonpolar overall.
In contrast, molecules such as SO₂, H₂S, NH₃, and PF₃ do not exhibit such symmetry and therefore, have a net dipole moment, making them polar molecules. For instance, SO₂ is bent, H₂S is angular, NH₃ is trigonal pyramidal, and PF₃ has a trigonal pyramidal shape with a lone pair on the phosphorus atom; all these aspects contribute to their polar nature.