Textbook Question
Predict whether each of the following molecules is polar or nonpolar: (a) IF, (b) CS2, (c) SO3, (d) PCl3, (e) SF6, (f) IF5.
Ch.9 - Molecular Geometry and Bonding Theories
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement146
- Ch.2 - Atoms, Molecules, and Ions200
- Ch.3 - Chemical Reactions and Reaction Stoichiometry176
- Ch.4 - Reactions in Aqueous Solution155
- Ch.5 - Thermochemistry126
- Ch.6 - Electronic Structure of Atoms131
- Ch.7 - Periodic Properties of the Elements126
- Ch.8 - Basic Concepts of Chemical Bonding123
- Ch.9 - Molecular Geometry and Bonding Theories143
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces91
- Ch.12 - Solids and Modern Materials122
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics174
- Ch.15 - Chemical Equilibrium101
- Ch.16 - Acid-Base Equilibria139
- Ch.17 - Additional Aspects of Aqueous Equilibria146
- Ch.18 - Chemistry of the Environment72
- Ch.19 - Chemical Thermodynamics129
- Ch.20 - Electrochemistry142
- Ch.21 - Nuclear Chemistry101
- Ch.22 - Chemistry of the Nonmetals68
- Ch.23 - Transition Metals and Coordination Chemistry66
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry10
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
Chapter 9, Problem 42
Predict whether each of the following molecules is polar or nonpolar: (a) CCl4, (b) NH3, (c) SF4, (d) XeF4, (e) CH3Br, (f) GaH3.
Verified step by step guidance1
1. To determine whether a molecule is polar or nonpolar, we first need to understand the concept of polarity. A molecule is polar if it has a net dipole moment. This happens when there is an imbalance in the electron distribution around the molecule, usually due to differences in electronegativity between the atoms.
2. For molecule (a) CCl4, look at the Lewis structure and molecular geometry. CCl4 has a tetrahedral shape with the carbon atom in the center and the four chlorine atoms surrounding it. The electronegativity difference between carbon and chlorine does create individual bond dipoles, but because of the symmetrical arrangement of these bonds, the dipoles cancel each other out, resulting in a nonpolar molecule.
3. For molecule (b) NH3, the nitrogen atom is in the center with three hydrogen atoms and one lone pair of electrons. The molecule has a trigonal pyramidal shape. The electronegativity difference between nitrogen and hydrogen creates a dipole, and because of the asymmetrical shape, these dipoles do not cancel out. Therefore, NH3 is a polar molecule.
4. For molecule (c) SF4, the sulfur atom is in the center with four fluorine atoms and one lone pair of electrons. The molecule has a see-saw shape. The electronegativity difference between sulfur and fluorine creates a dipole, and because of the asymmetrical shape, these dipoles do not cancel out. Therefore, SF4 is a polar molecule.
5. Repeat the same process for the remaining molecules (d) XeF4, (e) CH3Br, and (f) GaH3. Look at their Lewis structures, molecular geometries, and electronegativity differences to determine if they are polar or nonpolar.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Geometry
Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. The shape of a molecule significantly influences its polarity, as it determines how the dipole moments of individual bonds combine. For example, symmetrical shapes like tetrahedral or square planar can lead to nonpolar molecules, while asymmetrical shapes often result in polar molecules.
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Electronegativity
Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Differences in electronegativity between bonded atoms create dipole moments, where one end of the bond becomes partially negative and the other partially positive. This concept is crucial for determining the polarity of a molecule, as polar bonds contribute to an overall molecular dipole if the geometry is asymmetrical.
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Dipole Moment
A dipole moment is a vector quantity that represents the separation of positive and negative charges in a molecule. It is calculated as the product of the charge and the distance between the charges. Molecules with a net dipole moment are considered polar, while those with no net dipole moment are nonpolar. Understanding dipole moments helps predict the behavior of molecules in electric fields and their interactions with other substances.
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Related Practice
Textbook Question
a. Consider the AF3 molecules in Exercise 9.27. Which of these will have a nonzero dipole moment?
Textbook Question
Dichloroethylene (C2H2Cl2) has three forms (isomers), each of which is a different substance. (b) Which of these isomers has a zero dipole moment?
Textbook Question
(c) Does the molecule BF2Cl have a dipole moment?
Textbook Question
Dichlorobenzene, C6H4Cl2, exists in three forms (isomers) called ortho, meta, and para:
Which of these has a nonzero dipole moment?
Textbook Question
Dichloroethylene (C2H2Cl2) has three forms (isomers), each of which is a different substance. (c) How many isomeric forms can chloroethylene, C2H3Cl, have? Would they be expected to have dipole moments?