Lattice energy is a measure of the strength of the forces between the ions in an ionic solid. When comparing magnesium fluoride (MgF2) and magnesium oxide (MgO), magnesium oxide has a higher lattice energy.
The primary reason for this difference lies in the charges of the ions and the sizes of the ions involved. MgO consists of magnesium ions (Mg2+) and oxide ions (O2-), while MgF2 consists of magnesium ions (Mg2+) and fluoride ions (F–).
1. **Charge of the Ions:** The charges of the ions play a significant role in determining lattice energy. In MgO, both the magnesium and oxide ions have a charge of 2, resulting in a higher attractive force due to the greater charge product (2 * 2 = 4) compared to MgF2, where the charge product is (2 * 1 = 2).
2. **Size of the Ions:** Additionally, the ionic radii also affect the lattice energy. Oxygen ions (O2-) are smaller than fluoride ions (F–), which leads to closer packing of the ions in MgO. This close packing increases the electrostatic forces between the ions, further contributing to the higher lattice energy.
In summary, since MgO has ions with higher charges and smaller ionic radii compared to those in MgF2, it ultimately results in a stronger ionic bond, leading to a higher lattice energy for magnesium oxide.