Among the following which is the least basic

Options

A. `F^(-)`
B. `I^(-)`
C. `CI^(-)`
D. `Br^(-)`

Explanation

To determine which of the given elements (fluorine, iodine, chlorine, or bromine) is the least basic, we can analyze their basicity based on their electronegativity and size.

### Step-by-Step Solution:

1. **Understanding Basicity**: Basicity refers to the ability of an atom to donate a pair of electrons. In the context of halogens, basicity can be influenced by the electronegativity and size of the atoms.

2. **Electronegativity of Halogens**: Among the halogens, the electronegativity decreases as we move down the group in the periodic table. The order of electronegativity is:
- Fluorine (most electronegative)
- Chlorine
- Bromine
- Iodine (least electronegative)

3. **Stability and Size**: As we move down the group from fluorine to iodine, the size of the atoms increases. Larger atoms tend to be less basic because their outer electrons are farther from the nucleus and are held less tightly.

4. **Basicity Order**: The basicity of the halogens can be summarized as follows:
- Fluorine: Most basic (despite being the most electronegative, it is less stable)
- Chlorine: More basic than bromine and iodine
- Bromine: Less basic than chlorine but more basic than iodine
- Iodine: Least basic (due to its larger size and lower electronegativity)

5. **Conclusion**: Based on the analysis, iodine is the least basic among the given options.

### Final Answer:
**Iodine is the least basic element among fluorine, iodine, chlorine, and bromine.**