Group 2 hydrides with significant covalent character is/are

Options

A. `BeH_(2)`
B. `MgH_(2)`
C. `CaH_(2)`
D. Both (1) & (2)

Answer

To determine which Group 2 hydrides have significant covalent character, we can analyze the properties of the hydrides formed by the elements in Group 2 of the periodic table.

### Step-by-Step Solution:

1. **Identify Group 2 Elements**:
Group 2 elements include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba).

2. **Understand Hydride Formation**:
Group 2 elements typically form ionic hydrides due to their metallic nature. However, some exceptions exist where covalent character is significant.

3. **Examine Beryllium Hydride (BeH₂)**:
- Beryllium is small in size and has a high charge density (the charge-to-size ratio).
- Due to its small ionic radius and high charge, BeH₂ exhibits significant covalent character.

4. **Examine Magnesium Hydride (MgH₂)**:
- Magnesium is also relatively small compared to other Group 2 elements and has a higher charge density than larger Group 2 elements.
- Therefore, MgH₂ also shows significant covalent character.

5. **Examine Calcium Hydride (CaH₂)**:
- Calcium is larger than both beryllium and magnesium, leading to a lower charge density.
- As a result, CaH₂ is predominantly ionic and does not exhibit significant covalent character.

6. **Evaluate Other Options**:
- Strontium (SrH₂) and Barium (BaH₂) are even larger and more ionic than calcium hydride, thus they also do not exhibit significant covalent character.

7. **Conclusion**:
- The hydrides with significant covalent character in Group 2 are Beryllium Hydride (BeH₂) and Magnesium Hydride (MgH₂).
- Therefore, the correct answer is option 4: both 1 (Beryllium Hydride) and 2 (Magnesium Hydride).

### Final Answer:
The Group 2 hydrides with significant covalent character are Beryllium Hydride (BeH₂) and Magnesium Hydride (MgH₂), which corresponds to option 4.

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