Which of the following is correctly order regarding hydration enthalpies of alkaline earth metals ?

Options

A. `Be^(2+) lt Mg^(2+) lt Ca^(2+) lt Sr^(2+) lt Ba^(2+)`
B. `Be^(2+) gt Mg^(2+) gt Ca^(2+) gt Sr^(2+) gt Ba^(2+)`
C. `Be^(2+) lt Mg^(2+) gt Ca^(2+) gt Sr^(2+) gt Ba^(2+)`
D. `Mg^(2+) gt Be^(2+) gt Ca^(2+) lt Sr^(2+) gt Ba^(2+)`

Answer

To determine the correct order of hydration enthalpies of alkaline earth metals, we need to analyze the trend in hydration enthalpy as we move down the group in the periodic table.

### Step-by-Step Solution:

1. **Identify the Alkaline Earth Metals**:
The alkaline earth metals are Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). In their ionic forms, they are represented as Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺.

2. **Understand Hydration Enthalpy**:
Hydration enthalpy refers to the energy released when ions are surrounded by water molecules. It is influenced by the charge and size of the ion. Higher charge and smaller size typically lead to greater hydration enthalpy.

3. **Trend in Ionic Size**:
As we move down the group from Be to Ba, the size of the ions increases. This is due to the addition of electron shells, which increases the distance between the nucleus and the outer electrons.

4. **Trend in Hydration Enthalpy**:
Hydration enthalpy decreases down the group because the larger ions (like Ba²⁺) are less effectively surrounded by water molecules compared to smaller ions (like Be²⁺). Therefore, the order of hydration enthalpy from highest to lowest is:
- Be²⁺ > Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺

5. **Conclusion**:
The correct order regarding hydration enthalpies of alkaline earth metals is:
- Be²⁺ > Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺

### Final Answer:
The correct order regarding hydration enthalpies of alkaline earth metals is Be²⁺ > Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺.

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