Question

A student states “Polar molecules are just molecules that contain polar bonds. If there are no polar bonds, then the molecule is non-polar.” Do you agree or disagree with this statement? justify your reasoning from Model 1.

Answer 1

Polar molecules not only contain polar covalent bonds but must also have an asymmetric geometry that does not allow their bond dipole moments to cancel out, unlike nonpolar molecules which are symmetric.

Step-by-step explanation:

I disagree with the statement that "polar molecules are just molecules that contain polar bonds" because the overall polarity of a molecule is not solely based on the presence of polar bonds but also on the molecule's geometry. While it is true that a molecule can be polar if it contains at least one polar covalent bond, the molecule must also have an asymmetric shape so that the bond dipole moments do not cancel out.

For instance, carbon dioxide (CO2) has polar bonds, yet the molecule is nonpolar because it is linear and the dipole moments cancel each other. On the other hand, water (H2O) is polar because it has polar bonds and the molecule is bent, causing the dipole moments to add up, resulting in a net dipole moment.

Molecules like methane (CH4) are nonpolar because they lack polar bonds all together and have a symmetric tetrahedral shape. Hence, both the presence of polar bonds and molecular geometry determine the overall polarity of a molecule.