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.
Ch.8 - Basic Concepts of Chemical Bonding
Chapter 8, Problem 23d
The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (d) Using the lattice energies in Table 8.1, predict the lattice energy of ScN.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Isoelectronic Species
Isoelectronic species are atoms, ions, or molecules that have the same number of electrons and, consequently, the same electronic structure. For example, NaF and CaO both have the same number of valence electrons, which influences their chemical properties and interactions. Understanding isoelectronic relationships helps predict the behavior of compounds in terms of stability and reactivity.
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Lattice Energy
Lattice energy is the energy released when gaseous ions combine to form an ionic solid, or the energy required to separate one mole of a solid ionic compound into its gaseous ions. It is a measure of the strength of the forces between the ions in an ionic compound. Higher lattice energies indicate stronger ionic bonds, which can affect the stability and solubility of the compound.
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Trends in Lattice Energy
Lattice energy trends can be predicted based on ionic charge and ionic size. Generally, greater charges on the ions lead to higher lattice energies due to stronger electrostatic attractions, while larger ionic radii result in lower lattice energies due to increased distance between the charged ions. Understanding these trends is essential for predicting the lattice energy of compounds like ScN based on known values from similar compounds.
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Related Practice
Textbook Question
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Textbook Question
The substances NaF and CaO are isoelectronic (have the same number of valence electrons). (a) What are the charges on each of the cations in each compound?
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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
(a) Does the lattice energy of an ionic solid increase or decrease (i) as the charges of the ions increase, (ii) as the sizes of the ions increase?
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Textbook Question
Consider the ionic compounds KF, NaCl, NaBr, and LiCl. (a) Use ionic radii (Figure 7.8) to estimate the cation–anion distance for each compound.
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Textbook Question
Which of the following trends in lattice energy is due to differences in ionic radii? (a) LiF > NaF > CsF, (b) CaO > KCl, (c) PbS > Li2O.
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