Why is lithium fluoride insoluble in water?

Answer 1

it's the anomalous behaviour of Lithium because of its small size and high nuclear charge. Lithium exerts the greatest polarizing effect out of all the alkali metals on negative ion that may be the polerising in water molecule where oxygen aquire partial negetive charge and attach to lithium by electrostatic forces releasing larger amount of energy and therefore stable

Let me explain.
What is Hydration?
It is the dissoloution of the substance in water by adsorbing water molecule by weak valency forces.
Smaller the cation, greater is the degree of hydration.Alkali metals easily lose 1 electron therefore have high values of "oxidising potential" which means high tendency to get oxidised hence powerful reducing nature in aqueous medium.

It is a fact that Li+ has greatest reducing nature in aqueous medium due to maximum hydration energy for Li+ ion.

Answer 2

Lithium fluoride is insoluble in water because it has a greater ionic character than other lithium compounds for example lithium chloride and also the lattice energy is greater than the hydration enthalpy and therefore it cannot dissolve.

Note: for a ionic compound to dissolve the hydration enthalpy must be greater than or equal to the lattice energy of the compound.

Answer 3

Due to anomalous behaviour of fluorine.

The melting point of fluorine is not high: - 219,62 0C.

Answer 4

Extremely ionic bonding in the solid creates an ionic solid.

Answer 5

It is an ionic compound therefore there is a strong electrostatic attraction between oppositely charged ions.