Example problem 2.1 If the attractive force between a pair of Mg2tand S2- is 1.49X10-N and if the S2- ion has a radius of 0.184nm, calculate a value for the ionic radius of the Mg+ ion in nanometers Solution attractive 460a (2)(-2(1.60×10C a0-14 7 So Attractive V48.85×10C2/(N,m2)](.49×10N) =0.249mm 又:a Mg2+=a0-rs2=0249m-0.184m=0.065mExample problem 2.1 If the attractive force between a pair of Mg2+and S2- is 1.49×10-8N and if the S2- ion has a radius of 0.184nm, calculate a value for the ionic radius of the Mg2+ ion in nanometers. Solution 2 0 2 1 2 attractive 4 a Z Z e F    = − 0.249nm 4 [8.85 10 C (N m ](1.49 10 N) (2)( 2)(1.60 10 C) 4 1 2 2 2 8 1 9 2 0 attractive 2 1 2 0 =    − −  = −  = − − −   F  ） Z Z e a 2 2 0.249nm 0.184nm 0.065nm 2 2 M g 0 M g 0  = − = − = = + + − + − S S r a r 又a r r