Lithium salts are mostly hydrated like `LiCl*2H_(2)O` due to

Options

A. maximum ionisation enthalpy
B. maximum degree of hydration of `Li^(+)`
C. maximum hygroscopic nature
D. maximum chemical reactivity.

Explanation

To answer the question about why lithium salts are mostly hydrated, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Hydration**: Hydration refers to the process where water molecules surround and interact with ions. The extent of hydration depends on the ion's ability to attract water molecules.

2. **Identify Lithium's Position in the Alkali Metals**: Lithium (Li) is the smallest alkali metal. In the periodic table, it is positioned at the top of Group 1, which includes sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

3. **Charge Density of Lithium Ion**: The lithium ion (Li⁺) has a high charge density because it has a +1 charge and a relatively small ionic radius. Charge density is defined as the charge of the ion divided by its volume (or size). Since Li⁺ is smaller than other alkali metal ions, it has a higher charge density.

4. **Polarizing Power**: The high charge density of Li⁺ allows it to polarize water molecules effectively. Polarization occurs when the electric field of the ion distorts the electron cloud of the water molecules, leading to stronger interactions.

5. **Hydration Energy**: The energy released when water molecules surround an ion is known as hydration energy. The higher the charge density, the greater the hydration energy. Lithium, having the highest charge density among alkali metals, has the highest hydration energy.

6. **Comparison with Other Alkali Metals**: As we move down the group from lithium to cesium, the size of the ions increases, leading to a decrease in charge density and, consequently, a decrease in hydration energy. Therefore, other alkali metal ions (like Na⁺, K⁺, Rb⁺, and Cs⁺) do not hydrate as effectively as Li⁺.

7. **Conclusion**: Due to its high charge density and polarizing power, lithium salts, such as LiCl·2H₂O, are more likely to be hydrated compared to salts of other alkali metals, which tend to be anhydrous.

### Final Answer:
Lithium salts are mostly hydrated due to the high charge density of the lithium ion (Li⁺), which allows it to polarize water molecules effectively, resulting in higher hydration energy compared to other alkali metal ions.

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