Though covalent character increases form lithium fluoride to lithium iodide, lithium fluoride is insoluble in water while lithium iodide is soluble. Justify the above statement.

Explanation

Since the size of halide ion increase down the group, the ease of getting polarised by a cation also increases. Thus, `Li^(+)` ion can polarise `I^(-)` ion to a greater extent and thus from LiF to LiI covalent character increases. Hence, we expect that LiF is more soluble in water and LiI is less soluble or not soluble in water. The solubility of an ionic compound in water depends on the relative values of lattice energy and hydration energy. The substance becomes soluble in water if hydration energy exceeds lattice energy. From LiF to LiI, lattice energy decreases while hydration energy increases. Since lattice energy of LiF is much greater than hydration energy, it is insoluble in water and thus solubility in water increases from LiF to LiI.