Question

Aluminum oxide (Al2O3) is a widely used industrial abrasive (known as emery or corundum), for which the specific application depends on the hardness of the crystal. What does this hardness imply about the magnitude of the lattice energy? Would you have predicted from the chemical formula that Al2O3 is hard? Explain.

Answer 1

Answer:

On the Moh's scale of hardness, aluminum oxide is positioned just below to diamond due to which it is considered as one of the hardest known compounds. This also shows that the compound exhibit an enormous amount of lattice energy, as to transform the oxide into its constituent ions, the energy is required to overcome.  

Based on the chemical formula of the compound, that is, Al2O3, it is shown that the ions of Al3+ and O2- are kept close due to the activity of the strong electrostatic ionic bonds. The electrostatic forces and the ionic bonding between the ions are extremely robust due to the presence of the ions high charge density. Therefore, to dissociate the bonds, an enormous amount of energy is needed, and at the same time, a high amount of lattice energy is present.