Which of the following is paramagnetic ?

Options

A. `C_(2)^(2-)`
B. `Na_(2)O_(2)`
C. `NO_(2)`
D. CO

Answer

To determine which of the given species is paramagnetic, we need to analyze the number of electrons in each species. A species is considered paramagnetic if it has an odd number of electrons, while it is diamagnetic if it has an even number of electrons. Let's go through each option step by step.

### Step 1: Analyze Carbon (C)
- **Atomic Number of Carbon (C)**: 6
- **Total Electrons in 2 Carbon Atoms**:
\[ 2 \times 6 = 12 \text{ electrons} \]
- **Conclusion**: 12 is an even number, so Carbon is diamagnetic.

### Step 2: Analyze Sodium Peroxide (Na2O2)
- **Atomic Number of Sodium (Na)**: 11
- **Atomic Number of Oxygen (O)**: 8
- **Total Electrons Calculation**:
- Sodium contributes: \(2 \times 11 = 22\)
- Oxygen contributes: \(2 \times 8 + 2 \text{ (for O}^{2-}\text{)} = 16 + 2 = 18\)
- Total Electrons:
\[ 22 + 18 = 40 \text{ electrons} \]
- **Conclusion**: 40 is an even number, so Na2O2 is diamagnetic.

### Step 3: Analyze Nitrogen Dioxide (NO2)
- **Atomic Number of Nitrogen (N)**: 7
- **Total Electrons Calculation**:
- Nitrogen contributes: \(7\)
- Oxygen contributes: \(2 \times 8 = 16\)
- Total Electrons:
\[ 7 + 16 = 23 \text{ electrons} \]
- **Conclusion**: 23 is an odd number, so NO2 is paramagnetic.

### Step 4: Analyze Carbon Monoxide (CO)
- **Atomic Number of Carbon (C)**: 6
- **Atomic Number of Oxygen (O)**: 8
- **Total Electrons Calculation**:
- Carbon contributes: \(6\)
- Oxygen contributes: \(8\)
- Total Electrons:
\[ 6 + 8 = 14 \text{ electrons} \]
- **Conclusion**: 14 is an even number, so CO is diamagnetic.

### Final Conclusion
Based on the analysis:
- Carbon (C): Diamagnetic
- Sodium Peroxide (Na2O2): Diamagnetic
- Nitrogen Dioxide (NO2): Paramagnetic
- Carbon Monoxide (CO): Diamagnetic

Thus, the species that is paramagnetic is **NO2**.

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