Halogens react with each other to form a number of compounds called interhalogen compounds. Their genral formula is `AX_(n)`, where A is less electronegative halogen while X is a more electronegative halogen and n is its number. The interhalogen compounds are essentially covalent and more reactive than the halogens since the bond A-X is weaker than A-A or X-X bond. The reaction of interhalogens are similar to those of halogens.
Which of the following interhalogen compound is not possible ?

Options

A. `IF_(7)`
B. `IF_(5)`
C. `ClF_(3)`
D. `FBr_(3)`

Explanation

To determine which interhalogen compound is not possible, we need to analyze the given options based on the general formula for interhalogen compounds, which is \( AX_n \). Here, \( A \) is the less electronegative halogen, \( X \) is the more electronegative halogen, and \( n \) can be 1, 3, 5, or 7.

### Step-by-Step Solution:

1. **Understanding the Electronegativity Order**:
The electronegativity of halogens decreases down the group. The order is:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br) > Iodine (I)

2. **Evaluating Each Option**:
- **Option 1: IF7**
- Here, Iodine (I) is less electronegative than Fluorine (F).
- This follows the formula \( AX_n \) where \( A = I \) and \( X = F \), and \( n = 7 \).
- **Conclusion**: Possible.

- **Option 2: IF5**
- Again, Iodine (I) is less electronegative than Fluorine (F).
- This follows the formula \( AX_n \) where \( A = I \) and \( X = F \), and \( n = 5 \).
- **Conclusion**: Possible.

- **Option 3: ClF3**
- Chlorine (Cl) is less electronegative than Fluorine (F).
- This follows the formula \( AX_n \) where \( A = Cl \) and \( X = F \), and \( n = 3 \).
- **Conclusion**: Possible.

- **Option 4: FBr3**
- Here, Fluorine (F) is more electronegative than Bromine (Br).
- This does not follow the formula \( AX_n \) since \( A \) should be less electronegative than \( X \).
- **Conclusion**: Not possible.

3. **Final Answer**:
The interhalogen compound that is not possible is **Option 4: FBr3**.