Question

Which factors govern the magnitude of the lattice energy of an ionic compound?

a) Size of ions and charge on ions
b) Temperature and pressure
c) Presence of impurities
d) Atomic number of the elements involved

Answer 1

The magnitude of the lattice energy in ionic compounds is primarily influenced by the size of ions and the ionic charges, where smaller ions and higher charges result in greater lattice energy.

Step-by-step explanation:

The factors that govern the magnitude of the lattice energy of an ionic compound are primarily related to the size of ions and the charge on ions. Lattice energy, a measure of the strength of the forces between the ions in an ionic solid, increases as the charge on the ions increases and as the size of the ions decreases. Therefore, smaller ions and ions with greater charges result in stronger electrostatic attractions and subsequently higher lattice energy.

For example, the lattice energy of LiF, with a cation charge (Z*) and anion charge (Z¯) of 1, is 1023 kJ/mol. In contrast, MgO, with doubled charges (Z* and Z = 2), has a much higher lattice energy of 3900 kJ/mol; the increase in ionic charge leads to a quadrupling of lattice energy, given that the sizes of the ions are relatively constant.