For a $K^{+}-C{l}^{-}$ion pair, attractive and repulsive energies $E_A$ and $E_R,$ respectively, depend on the distance between the ions $r,$ according to

$E_A=\frac{-1\mathrm{.}436}{r}$

$E_R=\frac{5\mathrm{.}86{10}^{-6}}{r^9}$

For these expressions, energies are expressed in electron volts per $K^{+}-C{l}^{-}$pair, and $r$ is the distance in nanometers. The net energy $E_N$ is just the sum of the preceding two expressions.

$($b$)$ On the basis of this plot, determine $($i$)$ the equilibrium spacing ro between the K$*($in nm$)$ and Cl ions, and $($ii$)$ the magnitude of the bonding energy Eo between the two ions in $($eV$).$