For a Na*-Cl ion pair, attractive and repulsive energies EA and ER, respectively, depend on the distance between the ions r, according to E_{A}=-\frac{1.436}{r} \quad \text { and } \quad

E_{R}=\frac{7.32 \times 10^{-6}}{r^{8}} For these expressions, energies are expressed in electron volts (eV) per Na*–Cl¯ pair, and r is-the distance in nanometers (nm). The net energy En is just the sum of the preceding two expressions. (a) Superimpose on a single plot EN, ER, and EA versus r up to 1.0 nm. (b) On the basis of this plot, determine (i) the equilibrium spacing ro between the Na* and Cl-ions, and (ii) the magnitude of the bonding energy Eo between the two ions.