34. Calculate the lattice energy for Al2O3. Estimate the Born exponent based on the electron configurations of the ions.
The quantities needed to be estimated to use the Born-Landé equation are the Madelung constant, the Born exponent, and the internuclear distance between the Al3+ and the O2– ions.
The Madelung constant is found from Table 5.12 (DMA) to be 4.040.
The Born exponent is found from electron configurations: Al3+ and O2– both have the [Ne] electron configuration so n = 7.
The internuclear distance is the sum of the cationic (DMA Table 5.8, CN = 6) and anionic radii (DMA Table 5.10) = 67.5 + 126 = 193.5 pm.
Using these values:
Elat = 14910 kJ/mol