`CI- O` bond length is 170 pm in the oxyanion

Options

A. Hypochlorite
B. chlorite
C. chlorate
D. Perchlorate

Answer

To determine which oxyanion corresponds to a Cl-O bond length of 170 pm, we need to analyze the bond lengths in the given options: hypochlorite (ClO⁻), chlorite (ClO₂⁻), chlorate (ClO₃⁻), and perchlorate (ClO₄⁻).

### Step-by-Step Solution:

1. **Identify the Oxyanions**:
- Hypochlorite: ClO⁻
- Chlorite: ClO₂⁻
- Chlorate: ClO₃⁻
- Perchlorate: ClO₄⁻

2. **Understand the Concept of Resonance**:
- Resonance occurs when a molecule can be represented by two or more valid Lewis structures. In the case of chlorite, chlorate, and perchlorate, these ions can exhibit resonance, which leads to bond length variations.

3. **Analyze the Bond Lengths**:
- The bond length in a molecule is influenced by the presence of resonance. The more resonance structures an oxyanion has, the shorter and stronger the bonds tend to be due to delocalization of electrons.
- Hypochlorite (ClO⁻) does not participate in resonance, meaning it has a single bond character between Cl and O.

4. **Compare Bond Lengths**:
- For hypochlorite (ClO⁻), the Cl-O bond length is longer because it does not have resonance stabilization.
- For chlorite (ClO₂⁻), chlorate (ClO₃⁻), and perchlorate (ClO₄⁻), the Cl-O bond lengths are shorter due to resonance.

5. **Conclusion**:
- Given that the bond length of Cl-O is 170 pm, which is relatively longer, this bond length corresponds to hypochlorite (ClO⁻) as it does not participate in resonance, leading to a longer bond length compared to the other oxyanions.

### Final Answer:
The oxyanion with a Cl-O bond length of 170 pm is **hypochlorite (ClO⁻)**.