energies. The insolubility of lithium fluoride results from the high lattice energy which in this case is not exceeded by the combined hydration energies. Other Group I fluorides dissolve since the lattice energies are smaller and are exceeded by the combined hydration energies.
In this discussion, entropy factors have been ignored and in certain cases where the difference between lattice energy and hydration energy is small it is the entropy changes which determine whether a substance will or will not dissolve. Each case must be considered individually and the relevant data obtained (see Chapter 3), when irregular behaviour will often be found to have a logical explanation