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?
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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Key Concepts
Isoelectronic Species
Valence Electrons
Ionic Charges
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.
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?
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?
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.
(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?