Write increasing order of basic strength of following:
`(a) F^(Theta) " "(b) Cl^(Theta)" "(c) Br^(Theta)" "(d)I^(Theta)`

Answer

To determine the increasing order of basic strength of the given halide ions (F^-, Cl^-, Br^-, I^-), we need to consider the stability of these anions. The basic strength of an anion is inversely proportional to its stability; a more stable anion is less basic.

### Step-by-Step Solution:

1. **Understanding Basic Strength**: Basic strength refers to the ability of an ion to accept protons (H^+). The more stable the anion, the less likely it is to accept a proton, hence the weaker its basic strength.

2. **Analyzing Anion Stability**: The stability of an anion is influenced by its size. Larger anions can better disperse the negative charge, leading to greater stability.

3. **Order of Atomic Size**: The atomic size of the halogens increases as we move down the group in the periodic table:
- Fluorine (F) < Chlorine (Cl) < Bromine (Br) < Iodine (I)
- This means that I^- is the largest and F^- is the smallest.

4. **Stability of Anions**: Since larger anions can better stabilize the negative charge:
- I^- is the most stable (largest size)
- Br^- is less stable than I^-
- Cl^- is less stable than Br^-
- F^- is the least stable (smallest size)

5. **Basic Strength Order**: Since basic strength is inversely related to stability:
- F^- (least stable) > Cl^- > Br^- > I^- (most stable)

6. **Final Order**: Therefore, the increasing order of basic strength is:
- I^- < Br^- < Cl^- < F^-

### Conclusion:
The increasing order of basic strength of the given halide ions is:
**I^- < Br^- < Cl^- < F^-**