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 8.2. Based on the lattice energies, would you expect the Na¬Cl or the K¬F distance to be longer?
(b) Use the ionic radii given in Figure 7.7 to estimate the Na¬Cl and K¬F distances. Does this estimate agree with the prediction you made based on the lattice energies?

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Group 2A Group3A Group 6A Group 7A Be2+ 0.90 0.41 0.90 0.73 0.68 1.54 Ca2+ 114 1.82 1.96 Тег 2.07 Rb+ 0.94 206 Rb 2.11 1.92 144 cation anion neutral atom TABLE 8.2 Lattice Energies for Some Ionic Compounds Lattice Energy Lattice Energy Compound (kJ/mol) Compound(k)/mol) LiF LiCl Lil NaF NaCl NaBr Nal KF KCI KBr CsCl CsI MgCl2 SrCl2 2326 1030 834 730 910 788 732 682 808 701 671 657 600 2127 MgO CaO SrO 3795 3414 3217 ScN 7547