The property that matches with elements of the halogen family are:

Options

A. They are chemically highly reactive
B. They are metallic in nature
C. They are monoatomic in their molecular form
D. They have one electron in the valence shell

Explanation

To solve the question regarding the properties that match with elements of the halogen family, we will analyze each statement provided and determine its validity.

### Step-by-Step Solution:

1. **Identify the Halogen Family**:
- The halogen family consists of elements such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). These elements are known for their unique properties.

2. **Evaluate the First Statement**:
- **Statement**: "They are chemically highly reactive."
- **Analysis**: Halogens are indeed highly reactive due to their need to gain one electron to complete their valence shell (octet).
- **Conclusion**: This statement is **correct**.

3. **Evaluate the Second Statement**:
- **Statement**: "They are metallic in nature."
- **Analysis**: Halogens are non-metals, not metals. They do not exhibit metallic properties such as conductivity or malleability.
- **Conclusion**: This statement is **incorrect**.

4. **Evaluate the Third Statement**:
- **Statement**: "They are monoatomic in their molecular form."
- **Analysis**: Halogens exist primarily in diatomic molecular forms (e.g., F2, Cl2, Br2, I2) rather than as single atoms.
- **Conclusion**: This statement is **incorrect**.

5. **Evaluate the Fourth Statement**:
- **Statement**: "They have one electron in the valence shell."
- **Analysis**: Halogens have seven electrons in their valence shell (not one), which is why they are reactive; they need one more electron to achieve a stable octet.
- **Conclusion**: This statement is **incorrect**.

6. **Final Summary**:
- Out of the four statements evaluated, only the first statement regarding their reactivity is correct.

### Final Answer:
The property that matches with elements of the halogen family is that they are chemically highly reactive.

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