Among the following which is the least basic

Options

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

Explanation

To determine which of the given acids is the least basic, we need to analyze their conjugate bases and their stability. The basicity of a substance is inversely related to its acidity; hence, the more acidic a substance is, the less basic its conjugate base will be.

### Step-by-Step Solution:

1. **Identify the Acids**:
We have the following acids to consider: HF (hydrofluoric acid), HI (hydroiodic acid), HCl (hydrochloric acid), and HBr (hydrobromic acid).

2. **Determine the Conjugate Bases**:
The conjugate bases can be determined by removing a proton (H⁺) from each acid:
- HF → F⁻ (fluoride ion)
- HI → I⁻ (iodide ion)
- HCl → Cl⁻ (chloride ion)
- HBr → Br⁻ (bromide ion)

3. **Assess Stability of Conjugate Bases**:
The stability of the conjugate bases is crucial because the more stable the conjugate base, the more acidic the corresponding acid will be. The stability of the conjugate bases can be compared based on their ability to accommodate the negative charge:
- I⁻ (iodide) is the most stable due to its larger atomic size, which allows for better charge dispersion.
- Br⁻ (bromide) is less stable than I⁻ but more stable than Cl⁻.
- Cl⁻ (chloride) is less stable than Br⁻.
- F⁻ (fluoride) is the least stable due to its high electronegativity and small size, which does not allow for effective charge dispersion.

4. **Rank the Acidity**:
Based on the stability of the conjugate bases:
- HI is the most acidic (I⁻ is the most stable).
- HBr is next (Br⁻ is stable).
- HCl follows (Cl⁻ is less stable).
- HF is the least acidic (F⁻ is the least stable).

5. **Determine the Least Basic**:
Since basicity is inversely proportional to acidity, the acid with the highest acidity corresponds to the least basic conjugate base. Therefore, the least basic among the given options is the conjugate base of HI, which is I⁻.

### Conclusion:
The least basic among the given acids is **HI**, as its conjugate base (I⁻) is the most stable and thus the acid itself is the most acidic.