Textbook Question
NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (b) Use the ionic radii given in Figure 7.8 to estimate the Na─Cl and K─F distances.
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Ch.8 - Basic Concepts of Chemical Bonding
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 8, Problem 22a
NaCl and KF have the same crystal structure. The only difference between the two is the distance that separates cations and anions. (a) The lattice energies of NaCl and KF are given in Table 8.1. Based on the lattice energies, would you expect the Na─Cl or the K─F distance to be longer?
Verified step by step guidance1
Identify the relationship between lattice energy and ionic distance. Lattice energy is inversely proportional to the distance between ions; the greater the distance, the lower the lattice energy.
Look up the lattice energies for NaCl and KF in Table 8.1. Compare the values to determine which compound has the higher lattice energy.
Based on the comparison, determine which compound has the shorter ionic distance. The compound with the higher lattice energy will have the shorter distance between ions.
Conclude which ionic distance is longer based on the inverse relationship between lattice energy and ionic distance. If NaCl has a higher lattice energy than KF, then the Na─Cl distance is shorter, making the K─F distance longer, and vice versa.
Summarize the findings: The compound with the lower lattice energy will have the longer distance between its cations and anions.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lattice Energy
Lattice energy is the amount of energy released when gaseous ions combine to form an ionic solid. It is a measure of the strength of the forces between the ions in an ionic compound. Higher lattice energy indicates stronger ionic bonds, which typically results in shorter distances between cations and anions.
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00:49
Lattice Energy
Ionic Radius
Ionic radius refers to the size of an ion in a crystal lattice. Cations are smaller than their parent atoms due to the loss of electrons, while anions are larger due to the gain of electrons. The size of the ions affects the distance between them in the lattice structure, influencing the overall lattice energy.
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02:47Ionic Radius
Coulomb's Law
Coulomb's Law describes the electrostatic interaction between charged particles. It states that the force between two charged ions is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. This principle helps explain how the distance between ions affects lattice energy and stability.
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01:15Coulomb's Law Concept 2
Related Practice
Textbook Question
(a) Is lattice energy usually endothermic or exothermic?
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Textbook Question
(b) Write the chemical equation that represents the process of lattice energy for the case of NaCl.
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Textbook Question
(c) Would you expect salts like NaCl, which have singly charged ions, to have larger or smaller lattice energies compared to salts like CaO which are composed of doubly-charged ions?
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Textbook Question
The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (b) What are the charges of each of the anions in each compound?
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Textbook Question
The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (c) Without looking up lattice energies, which compound is predicted to have the larger lattice energy?