Textbook Question
(b) If you react BF3 to make the ion BF32-, is this ion planar?
Ch.9 - Molecular Geometry and Bonding Theories
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement140
- Ch.2 - Atoms, Molecules, and Ions192
- Ch.3 - Chemical Reactions and Reaction Stoichiometry172
- Ch.4 - Reactions in Aqueous Solution156
- Ch.5 - Thermochemistry151
- Ch.6 - Electronic Structure of Atoms137
- Ch.7 - Periodic Properties of the Elements127
- Ch.8 - Basic Concepts of Chemical Bonding143
- Ch.9 - Molecular Geometry and Bonding Theories167
- Ch.10 - Gases147
- Ch.11 - Liquids and Intermolecular Forces97
- Ch.12 - Solids and Modern Materials129
- Ch.13 - Properties of Solutions126
- Ch.14 - Chemical Kinetics175
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Acid-Base Equilibria127
- Ch.17 - Additional Aspects of Aqueous Equilibria133
- Ch.18 - Chemistry of the Environment88
- Ch.19 - Chemical Thermodynamics140
- Ch.20 - Electrochemistry137
- Ch.21 - Nuclear Chemistry99
- Ch.22 - Chemistry of the Nonmetals66
- Ch.23 - Transition Metals and Coordination Chemistry69
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry11
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
Chapter 9, Problem 36
Consider a molecule with the formula AX2. Supposing the A-X bond is polar, how would you expect the dipole moment of the AX2 molecule to change as the X-A-X bond angle decreases from 180° to 100°?
Verified step by step guidance1
Step 1: Understand the concept of dipole moment. The dipole moment is a measure of the separation of positive and negative charges in a molecule. It is a vector quantity, meaning it has both magnitude and direction.
Step 2: Consider the geometry of the AX2 molecule. When the X-A-X bond angle is 180°, the molecule is linear, and if the A-X bonds are equally polar, their dipole moments cancel each other out, resulting in a net dipole moment of zero.
Step 3: Analyze the effect of decreasing the bond angle. As the X-A-X bond angle decreases from 180° to 100°, the molecule becomes bent. This change in geometry affects the vector addition of the individual bond dipoles.
Step 4: Predict the change in dipole moment. With a bent geometry, the dipole moments of the A-X bonds no longer cancel completely. The net dipole moment becomes non-zero and increases as the bond angle decreases.
Step 5: Conclude the relationship. The dipole moment of the AX2 molecule increases as the X-A-X bond angle decreases from 180° to 100°, due to the change from a linear to a bent molecular shape, which prevents complete cancellation of the bond dipoles.
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. For a molecule with the formula AX2, the geometry can be linear at 180° or bent as the bond angle decreases. The shape influences how dipoles from polar bonds combine, affecting the overall dipole moment.
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Molecular Geometry with Two Electron Groups
Dipole Moment
The dipole moment is a measure of the separation of positive and negative charges in a molecule, represented as a vector quantity. It depends on both the magnitude of the charge and the distance between the charges. In polar molecules, the dipole moment can change with bond angles, as the orientation of the dipoles relative to each other alters the net dipole.
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01:25Dipole Moment
Bond Angle and Polarity
The bond angle in a molecule affects the vector sum of individual bond dipoles. As the bond angle decreases from 180° to 100°, the individual dipole moments of the A-X bonds do not cancel out as effectively, leading to an increase in the overall dipole moment. This change illustrates how molecular shape and bond angles influence molecular polarity.
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