13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
Polarity of chemical bonds happen in molecules when there is an unequal sharing of electrons.Â
Molecular Polarity
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concept
Molecular Polarity Concept 1
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When it comes to the idea of molecular polarity, we have to take into account perfect shapes versus non perfect shapes or imperfect shapes. We're going to stay here first recall that polarity of chemical bonds arises from unequal sharing of electrons between atoms based on electro negativity. Remember elements that are more electro negative will tend to attract electrons more towards themselves. Now we're going to say the molecular molecular polarity itself is just the polarity that arises for an entire molecule. And we're gonna say here we have non polar molecules and polar molecules as a result. Now, when we say non polar molecules were saying this is any hydrocarbon so composed of only carbon and hydrogen and any non hydrocarbon with the perfect shape. Now, when we say perfect shape, we break it down into perfect shape one versus perfect shape too. Now for perfect shape one, this is when our central element has the same surrounding elements and it has zero too long pairs. So you're central element has no long pairs on it. Our perfect shape to this happens when are central elements still has the same surrounding elements and it's either linear or square planner or planner. Okay, so that's the additional caveat for perfect shape too, we're going to say here that a polar molecule is any lewis dot structure that doesn't have a perfect shape. So if you're able to identify a perfect shape automatically, it's going to be non polar. And if you have a molecule that doesn't fit fit perfect shape one or two, it's by default polar
Both a molecule's shape and bond polarity can affect its overall polarity.
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Molecular Polarity Concept 2
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So remember if you are a perfect shaped one or perfect shape to you're going to be non polar by default. So if we take a look here, we have our number of electron groups around our central element. Remember an electron group is either a surrounding element or a lone pair on that central element. They're both classified as electron groups and our central element can either have zero lone pairs all the way up to three lone pairs. Now, if we take a look here, all those that are sheeted in green represent perfect shape Once all of them have a central element that is the black sphere and all of them have the same surrounding elements around them. And most importantly, the central element has no lone pairs. Okay, so everyone here in this ring column would be non polar here. If we look at these two orange backgrounds, we're gonna say those are also non polar because they represent are perfect shape. Twos they have our central element in the center and we have the same surrounding elements. So we're gonna assume that these fears here are the same surrounding elements and they are either linear. So this would be a linear shape or they are square, planner or planner. So they fit the whole idea of perfect shape too. That's why there are also non polar. The other ones that are not highlighted. If you have those shapes, there's no way we can make them non polar. They're always going to be polar molecules. All right. So if you get anything that's within this part here, which is not shaded in green or an orange, they're always going to be polar. So keep that in mind. Look to see if your molecule has a perfect shape, one or perfect shape, too. If it doesn't fit the criteria, it's non polar. If it doesn't, then it's going to be polar.
Perfect Shape I: When the central element has no lone pairs and has the same surrounding elements then usually the molecule is nonpolar.
Perfect Shape II: When the central element has same surrounding elements and has a linear or square planar geometry.
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Molecular Polarity Example 1
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here in this example question, it says determine of carbon tetrachloride, which is CCL four is poor or non polar. Alright, so here, remember when we draw lewis dot structures, we place the least electro negative element in the center. In this case it would be carbon carbon here is in Group four A. So it has four valence electrons. So we're gonna draw our four valence electrons, Our chlorine, our in group seven a. So they each have seven valence electrons. Oh and remember carbon wants to make four bonds or must make four bonds. So each chlorine will form a single bond with our carbon. Now, if we take a look at the structure, we're going to say that our central element has the same surrounding elements and it has no lone pairs on it, it would be defined as a perfect shape one and as as a result of being a perfect shape, it would be non polar. So if you were going to say that carbon tetrachloride is a non polar molecule.
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Problem
ProblemDetermine if the compound of BCl2F is polar or nonpolar.
A
polar
B
nonpolar
C
cannot be determined
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Problem
ProblemDetermine if phosphorus trihydride, PH3, is polar or nonpolar.
A
Polar
B
Nonpolar
C
Cannot be determined
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Problem
ProblemWhich of the following compounds is/are nonpolar?
I. COF2 II. ICl2– III. XeF4 IV. C8H18
A
I only
B
II, IV
C
I, III
D
II, III, IV
E
All of the above
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Problem
ProblemDetermine if disulfur dichloride, S2Cl2, is polar or nonpolar.
A
Polar
B
Nonpolar
C
Cannot be determined
Additional resources for Molecular Polarity
PRACTICE PROBLEMS AND ACTIVITIES (34)
- The molecule shown here is difluoromethane 1CH2F22, which is used as a refrigerant called R-32. (c) If the m...
- The molecules have the same molecular formula (C3H8O) but different chemical structures. (b) Which molecule d...
- Which molecule has polar bonds but is nonpolar? (LO 8.6) (a) SF6 (b) SF2 (c) F2 (d) NF3
- Ethyl acetate, CH3CO2CH2CH3, is commonly used as a solvent and nail-polish remover. Look at the following ele...
- The dipole moment of methanol is m = 1.70 D. Use arrows to indicate the direction in which electrons are displ...
- (a) Does CS2 have a dipole moment? If so, in which direction does the net dipole point?
- (a) Consider the following two molecules: PCl3 and BCl3. Which molecule has a nonzero dipole moment?
- Predict whether each of the following molecules is polar or nonpolar: (a) IF, (b) CS2, (c) SO3, (d) PCl3, (e) ...
- Predict whether each of the following molecules is polar or nonpolar: (a) CCl4, (b) NH3, (c) SF4, (d) XeF4, (e...
- Dichloroethylene 1C2H2Cl22 has three forms (isomers), each of which is a different substance. (b) Which of th...
- Dihydroxybenzene, C6H6O2, exists in three forms (isomers) called ortho, meta, and para: Which of these has...
- Explain why CO2 and CCl4 are both nonpolar even though they contain polar bonds.
- CH3F is a polar molecule, even though the tetrahedral geometry often leads to nonpolar molecules. Explain.
- Determine whether each molecule in Exercise 57 is polar or nonpolar. a. PF3 b. SBr2 c. CHCl3 d. CS2
- Determine whether each molecule in Exercise 58 is polar or nonpolar. a. CF4 b. NF3 c. OF2 d. H2S
- Determine whether each molecule is polar or nonpolar. c. BrCl5
- Determine whether each molecule is polar or nonpolar. b. SCl4
- Determine whether each molecule is polar or nonpolar. a. SiCl4 b. CF2Cl2 c. SeF6 d. IF5
- Which of the following substances would you expect to have a nonzero dipole moment? Explain, and show the dir...
- Draw three-dimensional structures of PCl3 and PCl5, and then explain why one of the molecules has a dipole mo...
- Of the two compounds SiF4 and SF4, which is polar and which is nonpolar?
- Fluorine is more electronegative than chlorine, yet fluoromethane 1CH3F; m = 1.86 D2 has a smaller dipole mome...
- Most vitamins can be classified as either fat soluble, which results in their tendency to accumulate in the b...
- Most vitamins can be classified as either fat soluble, which results in their tendency to accumulate in the bo...
- Fill in the blank spaces in the following chart. If the molecule column is blank, find an example that fulfill...
- Draw the structure of a molecule with the formula C4H6Cl2 that has a dipole moment of 0.
- Just as individual bonds in a molecule are often polar, molecules as a whole are also often polar because of t...
- Which formula represents a nonpolar molecule containing polar covalent bonds
- Predict whether each of the following molecules is polar or nonpolar.
- Which one of the following exhibits dipole-dipole attraction between molecules?
- Where, approximately, is the negative pole on each of these molecules?
- Water is known as a polar molecule because
- How many of the following molecules are polar
- Which of these af3 molecules will have a nonzero dipole moment?