The attractive energy E_A and repulsive energy E_R for a Na+ and Cl ion pair depends on the distance r between the ions, and is given by the following relation:

and

For these relationships, the energy is expressed as eV per K⁺ and Cl^- ion pair and r as ion distance in nm. The net energy E_N is the sum of the relationships above, E_N = E_A + E_R.

a)

Make a plot showing E_A, E_R, and E_N from -10 eV to 10 eV as a function of r from 0 to 1.2 nm.

b)

Using the diagram, find the equilibrium distance r₀ and the potential energy E₀.

c)

Calculate r₀ and E₀ and compare the values that you found from the curve.