Not every molecule with polar bonds is polar. Explain this statement. Use CCl©þ as an example.
A molecule must satisfy two criteria to be polar.
a)it must have polar bonds.
b)it must NOT be symmetrical in three dimensions.
CCl4 has C-Cl bonds that differ in electronegativity; therefore, each of the C-Cl bonds is polar.
However, the CCl4 molecule, as a whole, is symmetrical (tetrahedral); therefore, the individual polar bonds are canceled and the molecule as a whole is not polar. Contrast this with CHCl3. The H on one C-H bond doesn't cancel the three C-Cl bonds at the other angles so it WILL be polar as a molecule. Look at CO2, a simpler molecule because it is linear. But since it is O=C=O, the molecule is symmetrical, the individual C-O polarities cancel, and the CO2 molecule is not polar. But HCN is polar because the C-H polarity is not th same as the C-N polarity. I may be able to find something on the web that shows pictures if you still don't quite understand.
CCl(subscript 4) *
mhv
When we talk about polar molecules, we are referring to molecules that have a separation of positive and negative charges within the molecule. This occurs when the individual bond dipoles do not cancel each other out. In simple terms, a molecule can be polar if it has an uneven distribution of electrons due to differences in electronegativity between the atoms.
Now, let's use CCl₄ as an example to understand why not every molecule with polar bonds is polar. The molecule CCl₄ has polar bonds because there is a significant electronegativity difference between carbon (C) and chlorine (Cl). Chlorine is more electronegative than carbon, causing a dipole moment in each C-Cl bond, with partial negative charge on the chlorine atom and partial positive charge on the carbon atom.
However, despite having polar bonds, CCl₄ is a nonpolar molecule. This is because the four C-Cl bond dipoles in CCl₄ are arranged symmetrically around the carbon atom forming a tetrahedral shape. The bond dipoles cancel each other out, resulting in a net dipole moment of zero. Consequently, the molecule as a whole has no separation of charge and is considered nonpolar.
To determine the polarity of a molecule, it is important to consider not just the individual bond polarities but also the molecular geometry and the symmetry of the molecule. If the polar bonds are arranged symmetrically, as in the case of CCl₄, the molecule will be nonpolar, even though it has polar bonds.
Remember, the concept of molecular polarity can be further explored by considering the shape of the molecule and the electronegativity differences between the atoms involved in the bond formation.