Group 1 Elements

Lattice energy charge of ion
On moving downward, the size of alkaline earth metals increases due to increase in number of shells.
Thus, has the smallest size. Hence, lattice energy is highest for .

Lattice energy decreases with increase in ionic size. Since, ionic size of is minimum hence it has maximum lattice energy.

Basic character of hydroxides of -block elements increase with increasing atomic number. However alkaline earth metal hydroxides are less basic than alkali metal hydroxides. Therefore, is the weakest base.

Alkali metal hydroxides are the strongest of all bases and on moving down the group strength of the bases increases. Hence, is the strongest base.

In case of hydration energy is higher than the lattice energy. Hydration enthalpies of alkaline earth metal ions decrease with increase in ionic size down the group. Lattice energy also decreases as the size of cation increases. But in case of large size anion such as and the small changes in cation size do not alter the lattice energy, i.e., lattice energies are about the same. For and , hydration enthalpies of and ions are higher than that of their lattice enthalpies.

Solvay process is used for preparation of .
In this process, precipitate of is obtained,
which is filtered and heated up to obtain .
Step I

Step II
Step III
But in case of potassium, is soluble in water so it cannot be precipitated out.
Due to which its decomposition is not possible.
Hence, cannot be obtained from this process,

Higher is the hydration energy, more will be the solubility in water. If the cations have different charge then the one with higher charge will have higher hydration energy. Among and all of the cations have charge, so for comparing hydration energy size factor will be considered Smaller is the size more will be the hydration energy. Thus, among all cations is smallest in size. Hence , is most soluble in water