Recall that the polarity of chemical bonds arises from the unequal sharing of electrons between atoms based on electronegativity. We're going to say here that when we mention molecular polarity, we are talking about polarity that arises from an entire covalent molecule. With this idea, we have nonpolar versus polar molecules. Nonpolar molecules are any hydrocarbon, so compounds composed of only carbons and hydrogens, and any non-hydrocarbon with a perfect shape. Now, a compound has a perfect shape when the central element has 0 lone pairs and the same surrounding elements. If you break either one of those, then you are classified as a polar molecule. So that's any Lewis dot structure that doesn't have a perfect shape. Looking at the examples here, where there are 2 to 4 electron groups, in the first column, all of these shapes have 0 lone pairs on the central element, and it's assumed that all the surrounding elements would be the same. In these situations, all these molecules would be nonpolar. Once we start encountering cases where the central element has 1 lone pair, 2 lone pairs, etc., then all of these are classified as polar molecules. They no longer have perfect shapes. So, to be a perfect shape, your central element has to have 0 lone pairs, and the surrounding elements must be the same.
Molecular Polarity (Simplified) - Video Tutorials & Practice Problems
Polarity happen in molecules when there is an unequal sharing of electrons.
Molecular Polarity
Both a molecule's shape and bond polarity can affect its overall polarity.
Molecular Polarity (Simplified) Concept 1
Video transcript
Nonpolar Molecules posses perfect shape, while polar molecules do not.
Molecular Polarity (Simplified) Example 1
Video transcript
Determine if carbon tetrachloride CCl4 is polar or nonpolar. Alright. So we have carbon which is in group 4A, and chlorine which is in group 7A, and there are 4 of them, giving us 32 valence electrons total. Carbon will go in the center. It will form single bonds with the chlorines. Remember the surrounding elements have to follow the octet rule, so we put enough electrons around them to do that. And that takes care of our 32 valence electrons. Now we're going to say here that we have a molecule basically that we've drawn that has 4 bonding groups. Remember, bonding groups are just your surrounding elements, and it has 0 lone pairs. Here, our central element has no lone pairs, and we have the same surrounding elements. So this is a perfect shape. Since it's a perfect shape, that means the molecule will be nonpolar.
Determine if the compound of BCl2F is polar or nonpolar.
Determine if phosphorus trihydride, PH3, is polar or nonpolar.
Determine if difluorine selenide, F2Se, is polar or nonpolar.
Determine if carbon dioxide, CO2, is polar or nonpolar.
Do you want more practice?
Your GOB Chemistry tutor
- Why is CCl₄ a nonpolar molecule, but is PCl₃ a polar molecule?
- Match each of the Lewis structures (a to c) with the correct diagram (1 to 3) of its shape, and name the shape...
- Match each of the formulas (a to c) with the correct diagram (1 to 3) of its shape, and name the shape; indica...
- Predict the shape and polarity of each of the following molecules, which have polar covalent bonds: (6.8, 6.9)...