The lattice energy of magnesium oxide (MgO) can be calculated using the Born-Haber cycle, which is a thermochemical cycle that relates various energetic steps involved in the formation of an ionic compound from its elements.
To determine the lattice energy, we consider the following steps:
- Formation of gaseous magnesium ions (Mg2+): This involves the ionization of solid magnesium to form magnesium ions:
- Formation of gaseous oxide ions (O2-): This step includes the process of gaining electrons by oxygen atoms:
- Combining gasses magnesium ions and oxide ions to form solid MgO:
Mg(s) → Mg2+(g) + 2e-
O(g) + 2e- → O2-(g)
Mg2+(g) + O2-(g) → MgO(s)
The overall energy change from these steps will give us the lattice energy.
For MgO, a commonly accepted value for its lattice energy is around -3920 kJ/mol. This negative sign indicates that energy is released when the oppositely charged ions come together to form a stable ionic compound.
In summary, the lattice energy of magnesium oxide indicates the strength of the ionic bond formed and reflects the energy required to separate the ions in the solid structure back into gaseous form.