In which of the following unpaired electron reside in unhybridised orbital

Options

A. `ClO_(2)`
B. `ClO_(3)`
C. `NO_(2)`
D. None of these

Answer

To determine in which of the given compounds the unpaired electron resides in an unhybridized orbital, we will analyze the molecular structures of ClO2, ClO3^-, and NO2 step by step.

### Step 1: Analyze ClO2
1. **Valence Electrons**: Chlorine (Cl) has 7 valence electrons and each oxygen (O) has 6 valence electrons. Therefore, for ClO2:
- Total valence electrons = 7 (from Cl) + 2 × 6 (from O) = 19 electrons.

2. **Lewis Structure**:
- Chlorine forms a double bond with one oxygen and a single bond with the other oxygen.
- The structure can be represented as:
```
O
||
Cl - O
```
- After forming bonds, the remaining electrons on Cl will be 3 (7 - 4 = 3).
- This results in 1 lone pair and 1 unpaired electron on Cl.

3. **Conclusion for ClO2**:
- ClO2 has an unpaired electron in an unhybridized p orbital.

### Step 2: Analyze ClO3^-
1. **Valence Electrons**: For ClO3^-:
- Total valence electrons = 7 (from Cl) + 3 × 6 (from O) + 1 (extra for the negative charge) = 25 electrons.

2. **Lewis Structure**:
- Chlorine forms double bonds with two oxygens and a single bond with one oxygen.
- The structure can be represented as:
```
O
||
O - Cl - O
```
- After forming bonds, the remaining electrons on Cl will be 1 lone pair and no unpaired electrons.

3. **Conclusion for ClO3^-**:
- ClO3^- does not have any unpaired electrons.

### Step 3: Analyze NO2
1. **Valence Electrons**: For NO2:
- Total valence electrons = 5 (from N) + 2 × 6 (from O) = 17 electrons.

2. **Lewis Structure**:
- Nitrogen forms a double bond with one oxygen and a single bond with the other oxygen.
- The structure can be represented as:
```
O
||
N - O
```
- After forming bonds, nitrogen will have 1 lone pair and 1 unpaired electron.

3. **Conclusion for NO2**:
- NO2 has an unpaired electron, but it is in a hybridized orbital due to the sp2 hybridization of nitrogen.

### Final Conclusion
- The only compound where the unpaired electron resides in an unhybridized orbital is **ClO2**.