A Q:4 For an NaCl ion pair, attractive and repulsive energies E A and Er respectively, depend on the distance between the ions r, according to = EA= - 1.436/r ER= 7.32* 10/r8 For these expressions, energies are expressed in electron volts per pair NaCl, and r is the distance in nanometers. The net energy En is just the sum of the two expressions above. (a) Superimpose on a single plot En , EA , Er and versus r up to 1.0 nm. > (b) On the basis of this plot, determine (i) the equilibrium spacing ro between the Na* and CI ions, and (ii) the magnitude of the bonding energy E, between the two ions. (c) Mathematically determine the ro and values using the solutions to Problem 2.14 and compare these with the graphical results from part (b)