23.57 - An Ionic Crystal. Figure P23.57Figure P23.57 shows eight pointcharges arranged at the comersof a cube with sides of length d.The values of the charges are+q and -q, as shown. This is+9a model of one cell of a cubicionic crystal. In sodium chloride(NaCI), for instance, the posi-tive ions are Na* and the nega-tive ions are CI". (a) Calculatethe potential energy U of thisarrangement. (Take as zero thepotential energy of the eight charges when they are infinitely farapart.) (b) In part (a), you should have found that U < 0. Explainthe relationship between this result and the observation that suchionic crystals exist in nature.

23.57 - Án Ionic Crystal. Figure P23.57 Figure P23.57 shows eight point charges arranged at the comers of a cube with sides of length d. The values of the charges are +q and -q, as shown. This is a model of one cell of a cubic +9 ionic crystal. In sodium chloride (NaCI), for instance, the posi- tive ions are Na* and the nega- tive ions are Cr". (a) Calculate the potential energy U of this arrangement. (Take as zero the potential energy of the eight charges when they are infinitely far apart.) (b) In part (a), you should have found that U < 0. Explain the relationship between this result and the observation that such ionic crystals exist in nature. ta

23.57 - Án Ionic Crystal. Figure P23.57 Figure P23.57 shows eight point charges arranged at the comers of a cube with sides of length d. The values of the charges are +q and -q, as shown. This is a model of one cell of a cubic +9 ionic crystal. In sodium chloride (NaCI), for instance, the posi- tive ions are Na* and the nega- tive ions are Cr". (a) Calculate the potential energy U of this arrangement. (Take as zero the potential energy of the eight charges when they are infinitely far apart.) (b) In part (a), you should have found that U < 0. Explain the relationship between this result and the observation that such ionic crystals exist in nature. ta