Recall that the polarity of chemical bonds arises from unequal sharing of electrons between atoms based on electronegativity. When we discuss molecular polarity, we are referring to polarity that arises from an entire covalent molecule. In this context, we differentiate between nonpolar and polar molecules. Nonpolar molecules are any hydrocarbon, meaning compounds composed of only carbons and hydrogens, and any non-hydrocarbon with a perfect shape. A compound has a perfect shape when the central element has 0 lone pairs and the same surrounding elements. If either criterion is not met, then the molecule is classified as a polar molecule. Hence, any Lewis dot structure that doesn't have a perfect shape falls into this category. For example, consider molecules with 2 to 4 electron groups. In the first column, all these shapes have 0 lone pairs on the central element, and it's assumed that all the surrounding elements are identical. In these cases, all these molecules would be nonpolar. Once we start considering a central element with 1 lone pair, 2 lone pairs, etc., these are classified as polar molecules due to their imperfection in shape. Therefore, to be a perfect shape, the central element must have 0 lone pairs, and the surrounding elements must be identical.
Molecular Polarity (Simplified) - Online Tutor, Practice Problems & Exam Prep
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.
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