Kotz & Treichel
    Chapter 9: 33, 35
 

Additional Problems
 

1) Using the Born-Mayer equation, estimate the lattice energy for the ionic solid CaO. The ionic radii for the relevant ions are: Ca²⁺ 114 pm, O^2- 126 pm. CaO has the NaCl structure (A=1.74756).

2) Based on your answer above, use a Born-Haber cycle to calculate the second electron affinity for oxygen, i.e., the DH for the reaction O^- + e^- =  O^2-. The enthalpy of vaporization for calcium is 201 kJ/mol and the enthaply of O₂ dissociation (O₂ = 2 O) is 249 kJ/mol. Additional required information is in your texts.

3) From your calculated second electron affinity, comment on the "inherent" stability of the O^2- ion. Is this in accord with the "octet rule" or not? If not, explain why the O^2- is considered to be so stable.