•• Figure 12.6 shows the energy E(R) for the Na+ and Cl− ions that make up the NaCl molecu...

•• Figure 12.6 shows the energy E(R) for the Na+ and Cl− ions that make up the NaCl molecule. Near its minimum at R0, E(R) can be approximated by a parabola: . Use the information on the graph to make a rough estimate of the force constant k. [Hint: To the left of R0, the graph retains a reasonably parabolic shape as far as the point where it crosses the horizontal axis.]