Which of the following is least reactive:

Options

A. F
B. Br
C. Cl
D. I

Explanation

To determine which of the following halogens is the least reactive, we need to analyze the reactivity trends of the halogens in Group 17 of the periodic table. The halogens include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step-by-Step Solution:

1. **Identify the Group**: Recognize that all the elements in the question are halogens, which belong to Group 17 of the periodic table.

2. **List the Halogens**: Write down the halogens in order of their atomic number:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)

3. **Understand Reactivity Trends**:
- Reactivity of halogens generally decreases as you move down the group in the periodic table. This is due to two main factors:
- **Electronegativity**: As you go down the group, electronegativity decreases.
- **Atomic Size**: The size of the atoms increases down the group, making it harder for larger atoms to attract electrons.

4. **Analyze Each Halogen**:
- **Fluorine**: Most reactive due to high electronegativity and small size.
- **Chlorine**: Less reactive than fluorine but still quite reactive.
- **Bromine**: Less reactive than chlorine.
- **Iodine**: Least reactive due to low electronegativity and larger atomic size.

5. **Conclusion**: Based on the trends observed, iodine (I) is the least reactive halogen among the options provided.

### Final Answer:
**Iodine (I) is the least reactive halogen.**

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