**Unformatted text preview: **2.12 The attractive force between two ions F A is just the derivative with respect to the interatomic separation of the attractive energy expression, Equation (2.8), which is just F A = dE A dr = d ( )- A r dr = A r 2 The constant A in this expression is defined in footnote 3 on page 21. Since the valences of the K + and O 2-ions are +1 and -2, respectively, Z 1 = 1 and Z 2 = 2, then F A = (Z 1 e )(Z 2 ) 4 πε o r 2 = (1)(2)(1.6 x 10-19 C) 2 (4)( π )(8.85 x 10-12 F/m)(1.5 x 10-9 m) 2 = 2.05 x 10-10 N 2.13 (a) Differentiation of Equation (2.11) yields dE N dr = A r (1 + 1)- nB r (n + 1) = 0...

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