Chapter 21, Problem 35P

SSM In crystals of the salt cesium chloride, cesium ions Cs⁺ form the eight corners of a cube and a chlorine ion Cl⁻ is at the cube’s center (Fig. 21-36). The edge length of the cube is 0.40 nm. The Cs⁺ ions are each deficient by one electron (and thus each has a charge of +e), and the Cl⁻ ion has one excess electron (and thus has a charge of −e). (a) What is the magnitude of the net electrostatic force exerted on the Cl⁻ ion by the eight Cs⁺ ions at the corners of the cube? (b) If one of the Cs⁺ ions is missing, the crystal is said to have a defect; what is the magnitude of the net electrostatic force exerted on the Cl⁻ ion by the seven remaining Cs⁺ ions?

Figure 21-36 Problem 35.