Lithium is the strongest reducing agent though it has highest ionisation enegy in its group. Which of the followinng factors is responsible for making Li the strongest reducing agent?

Options

A. Large heat of atomisation
B. Smaller size
C. Large sublimation energy
D. Large amount of hydration enthalpy

Explanation

To understand why lithium is the strongest reducing agent despite having the highest ionization energy in its group, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom or ion. For lithium (Li), this energy is relatively high compared to other alkali metals in its group.

2. **Formation of Lithium Ion (Li⁺)**:
- When lithium acts as a reducing agent, it loses an electron to form a lithium ion (Li⁺). This process requires energy, which is the ionization energy.

3. **Hydration Energy**:
- After lithium loses an electron and forms Li⁺, it can interact with water molecules. The energy released when water molecules surround and stabilize the Li⁺ ion is known as hydration energy.

4. **Comparison of Energies**:
- To determine the overall favorability of the reaction, we compare the ionization energy (energy input) with the hydration energy (energy output). If the hydration energy is significantly higher than the ionization energy, the process is favorable.

5. **Charge Density of Lithium**:
- Lithium has the highest charge density among the alkali metals. This is because it has a small ionic radius and a +1 charge. The small size leads to a greater attraction between the Li⁺ ion and water molecules, resulting in a high hydration energy.

6. **Conclusion**:
- The large hydration energy compensates for the high ionization energy, making the overall process energetically favorable. Thus, lithium can easily donate its electron and act as the strongest reducing agent in its group.

### Final Answer:
The factor responsible for making lithium the strongest reducing agent is its high hydration energy, which is a result of its high charge density.