The hydration energy of `Mg^(2+)` is larger than that of

Options

A. `Al^(3+)`
B. `Na^+`
C. `Be^(2+)`
D. `K^+`

Answer

To determine which ion has a hydration energy smaller than that of \( \text{Mg}^{2+} \), we need to analyze the factors affecting hydration energy.

### Step-by-Step Solution:

1. **Understanding Hydration Energy**:
- Hydration energy is the energy released when ions are surrounded by water molecules. It is influenced by the charge and size of the ion.
- Generally, smaller ions with higher charges have larger hydration energies because they can attract more water molecules due to their strong positive charge.

2. **Comparing Ions**:
- We need to compare \( \text{Mg}^{2+} \) with other ions (like \( \text{Na}^{+}, \text{K}^{+}, \text{Ca}^{2+}, \text{Al}^{3+} \), etc.) to find which has a smaller hydration energy.
- \( \text{Mg}^{2+} \) is a small ion with a +2 charge.

3. **Analyzing the Given Options**:
- **Option A: \( \text{Na}^{+} \)** - Sodium ion is larger than \( \text{Mg}^{2+} \) and has a +1 charge, so it will have a smaller hydration energy.
- **Option B: \( \text{K}^{+} \)** - Potassium ion is larger than sodium and also has a +1 charge, leading to even smaller hydration energy.
- **Option C: \( \text{Ca}^{2+} \)** - Calcium ion is larger than \( \text{Mg}^{2+} \) but also has a +2 charge, which may lead to comparable hydration energy.
- **Option D: \( \text{Al}^{3+} \)** - Aluminum ion is smaller than \( \text{Mg}^{2+} \) and has a +3 charge, likely resulting in a larger hydration energy.

4. **Conclusion**:
- Among the options, \( \text{Na}^{+} \) is the smallest ion with a +1 charge, which means it has a smaller hydration energy than \( \text{Mg}^{2+} \).
- Therefore, the hydration energy of \( \text{Mg}^{2+} \) is larger than that of \( \text{Na}^{+} \).

### Final Answer:
The hydration energy of \( \text{Mg}^{2+} \) is larger than that of \( \text{Na}^{+} \).

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