Which of the following is a pseudohalide?

Options

A. `I_3^-`
B. `IF_7`
C. `CN^-`
D. ICI

Answer

To determine which of the following options is a pseudohalide, we need to understand what a pseudohalide is. A pseudohalide is an anion that has properties similar to halogens but is not a true halogen. Pseudohalides often contain nitrogen.

Let's analyze the given options:

1. **I3- (Triiodide ion)**: This ion contains iodine, which is a halogen. Therefore, it is not a pseudohalide.

2. **IF7 (Iodine heptafluoride)**: This compound contains iodine and fluorine, both of which are halogens. Thus, it is also not a pseudohalide.

3. **CN- (Cyanide ion)**: This ion contains carbon and nitrogen. Since it contains nitrogen and has properties similar to halogens, it qualifies as a pseudohalide.

4. **ICL (Iodine monochloride)**: This compound contains iodine and chlorine, both of which are halogens. Therefore, it is not a pseudohalide.

From this analysis, we can conclude that the only pseudohalide among the options is **CN- (Cyanide ion)**.

### Final Answer:
The correct option is **CN- (Cyanide ion)**.