Consider the ionic salt, KCl (potassium chloride). The attractive and repulsive energies between the ions K+ and Cl depend on the distance r between them according to the following relationships:

Er=5.86x10-6/r^9
Ea = -1.436/r
En = EA +ER

where the energies are expressed in electron volts (eV) and the distance r is in nanometers (10°m). Eis the net potential energy between the ions.

(a) Using Excel, superimpose on a single plot EN, ER, and EA versus r, for r from 0.22nm to 0.5nm. Build the spreadsheet first and then plot the functions. Hint: Use a fine enough interval between r values such that you can see a minimum EN value.
(b) On the basis of this plot, determine (i) the equilibrium spacing r0 between the K+ and Cl– ions, and (ii) the magnitude of the bonding energy E0 between the two ions.
(c) Mathematically determine the r0 and E0values using the equations above and compare these with the graphical results from part (b)