Which of the following interhalogen compounds is not possible?

Solution

1. Interhalogen compounds are represented by the general formula ${\text{XX}}_n^{\prime }$ where $\text{X}$ is the larger halogen.
2. The value of $n$ can only be 1, 3, 5, or 7 based on the valence shell expansion.
3. ${\text{IF}}_8$ would require an oxidation state of +8 for iodine, which is not possible.
4. Hence the answer is (D).