Select the correct order of hydration energy of ions?

Options

A. `Li^(+)gtNa^(+)gtK^(+)`
B. `Li^(+)gtK^(+)gtNa^(+)`
C. `Cs^(+)gtRb^(+)gtK^(+)`
D. `Li^(+)gtCs^(+)gtK^(+)`

Explanation

To determine the correct order of hydration energy of ions from the group 1 series (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺), we need to consider the factors that influence hydration energy.

### Step-by-Step Solution:

1. **Understanding Hydration Energy**: Hydration energy refers to the energy released when an ion is surrounded by water molecules. It is influenced by the charge of the ion and its size (radius).

2. **Charge Consideration**: All the ions in the group 1 series (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) have the same charge (+1). Therefore, the charge does not play a role in differentiating their hydration energies.

3. **Size of Ions**: The size of the ions increases as we move down the group from lithium to cesium. The order of ionic radii is:
- Li⁺ < Na⁺ < K⁺ < Rb⁺ < Cs⁺
This means that lithium has the smallest radius and cesium has the largest radius.

4. **Hydration Energy Trend**: Hydration energy is inversely proportional to the size of the ion. This means:
- Smaller ions (with smaller radii) will have higher hydration energy because they can interact more strongly with water molecules.
- Larger ions (with larger radii) will have lower hydration energy.

5. **Order of Hydration Energy**: Based on the size of the ions, the order of hydration energy from highest to lowest is:
- Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺

6. **Conclusion**: The correct order of hydration energy of the ions is:
- Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺

### Final Answer:
The correct order of hydration energy of the ions is:
**Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺**