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 compounds is paramagnetic, we need to analyze the electronic configurations and the presence of unpaired electrons in each compound. Paramagnetic substances have one or more unpaired electrons, while diamagnetic substances have all electrons paired.

### Step-by-Step Solution:

1. **Understanding Paramagnetism**:
- Paramagnetic substances have unpaired electrons.
- Diamagnetic substances have all electrons paired.

2. **Analyzing the Options**:
- We will analyze each compound provided in the question to check for unpaired electrons.

3. **Option 1: C2 2-**:
- Carbon (C) has 4 valence electrons.
- In C2, the electronic configuration can be represented as:
- C: 1s² 2s² 2p²
- For C2, we have a total of 8 electrons (4 from each carbon).
- The molecular orbital configuration shows that all electrons are paired.
- Therefore, C2 2- is **diamagnetic**.

4. **Option 2: Na2O2**:
- Sodium (Na) has 1 valence electron, and Oxygen (O) has 6 valence electrons.
- In Na2O2, the structure shows that all electrons are paired:
- Na: 1s² 2s² 2p⁶ 3s¹ (1 valence electron)
- O: 1s² 2s² 2p⁴ (6 valence electrons)
- All electrons in Na2O2 are paired.
- Therefore, Na2O2 is **diamagnetic**.

5. **Option 3: NO2**:
- Nitrogen (N) has 5 valence electrons, and Oxygen (O) has 6 valence electrons.
- In NO2, the structure shows:
- N: 1s² 2s² 2p³ (5 valence electrons)
- O: 1s² 2s² 2p⁴ (6 valence electrons)
- When drawing the Lewis structure, one of the electrons from nitrogen remains unpaired.
- Therefore, NO2 is **paramagnetic**.

6. **Option 4: CO**:
- Carbon (C) has 4 valence electrons, and Oxygen (O) has 6 valence electrons.
- In CO, the structure shows:
- C: 1s² 2s² 2p² (4 valence electrons)
- O: 1s² 2s² 2p⁴ (6 valence electrons)
- All electrons in CO are paired.
- Therefore, CO is **diamagnetic**.

### Conclusion:
The only compound that is paramagnetic among the options provided is **NO2**.