Which one of the following are pseudohalide ions ?

Options

A. `CNO^(Theta)`
B. `OCN^(Theta)`
C. `RCOO^(Theta)`
D. `N_(3)^(Theta)`

Answer

To determine which of the given options are pseudohalide ions, we first need to understand the definition of pseudohalide ions. Pseudohalide ions are ions that consist of two or more electronegative atoms, with at least one of those atoms being nitrogen. They exhibit properties similar to halide ions.

Let's analyze the options provided:

1. **CNO⁻ (Cyanate ion)**:
- This ion consists of carbon (C), nitrogen (N), and oxygen (O).
- It contains nitrogen and is made up of electronegative atoms.
- Therefore, CNO⁻ qualifies as a pseudohalide ion.

2. **OCN⁻ (Isocyanate ion)**:
- This ion also consists of oxygen (O), carbon (C), and nitrogen (N).
- It contains nitrogen and is made up of electronegative atoms.
- Thus, OCN⁻ qualifies as a pseudohalide ion.

3. **RCOO⁻ (Carboxylate ion)**:
- This ion consists of a carbon (C) and two oxygen (O) atoms, but does not contain nitrogen.
- Since it does not have nitrogen, RCOO⁻ does not qualify as a pseudohalide ion.

4. **N³⁻ (Azide ion)**:
- This ion is composed entirely of nitrogen atoms.
- Although it consists of only nitrogen, it can still be classified as a pseudohalide ion because it meets the criteria of having electronegative atoms (in this case, nitrogen).

Now, summarizing the findings:
- CNO⁻ (pseudohalide ion)
- OCN⁻ (pseudohalide ion)
- RCOO⁻ (not a pseudohalide ion)
- N³⁻ (pseudohalide ion)

Thus, the pseudohalide ions from the options are CNO⁻, OCN⁻, and N³⁻.

**Final Answer**: CNO⁻, OCN⁻, and N³⁻ are the pseudohalide ions.