Arrang the anions (p) `overset(-)CH_(3),(q)overset(-)NH_(2),(r)OH^(-), (s)F^(-),` in decreasing order of their basic strength .

Options

A. `pgtqgtrgts`
B. `qgtpgtrgts`
C. `rgtqgtpgts`
D. `rgtpgtqgts`

Explanation

To arrange the anions \( \overset{-}{CH_3} \), \( \overset{-}{NH_2} \), \( OH^{-} \), and \( F^{-} \) in decreasing order of their basic strength, we can follow these steps:

### Step 1: Understand Basic Strength
Basic strength refers to the ability of an anion to donate a pair of electrons. The more readily an anion can donate its electrons, the stronger the base it is.

### Step 2: Analyze the Anions
We have the following anions:
- \( \overset{-}{CH_3} \) (methyl anion)
- \( \overset{-}{NH_2} \) (amide anion)
- \( OH^{-} \) (hydroxide anion)
- \( F^{-} \) (fluoride anion)

### Step 3: Consider Electronegativity
Electronegativity plays a crucial role in determining basic strength. The more electronegative an atom is, the more it attracts electrons towards itself, making it less likely to donate electrons. The electronegativity order for the relevant atoms is:
- Fluorine (F) > Oxygen (O) > Nitrogen (N) > Carbon (C)

### Step 4: Rank the Anions Based on Electronegativity
1. **\( \overset{-}{CH_3} \)**: The carbon atom is the least electronegative among the four, making it the most basic.
2. **\( \overset{-}{NH_2} \)**: Nitrogen is more electronegative than carbon but less than oxygen and fluorine, making it the second most basic.
3. **\( OH^{-} \)**: Oxygen is more electronegative than nitrogen, thus it is less basic than \( \overset{-}{NH_2} \).
4. **\( F^{-} \)**: Fluorine is the most electronegative element, making it the least basic as it holds onto its electrons tightly.

### Step 5: Final Arrangement
Based on the analysis, the decreasing order of basic strength is:
1. \( \overset{-}{CH_3} \) (most basic)
2. \( \overset{-}{NH_2} \)
3. \( OH^{-} \)
4. \( F^{-} \) (least basic)

### Final Answer
The correct order of the anions in decreasing order of their basic strength is:
\[ \overset{-}{CH_3} > \overset{-}{NH_2} > OH^{-} > F^{-} \]