Which one of the following molecules is expected to exhibit diamagnetic behaviour?

Options

A. `N_(2)`
B. `O_(2)`
C. `S_(2)`
D. `C_(2)`

Answer

To determine which of the given molecules exhibits diamagnetic behavior, we need to analyze their electronic configurations and the presence of unpaired electrons. Diamagnetic substances are characterized by having all their electrons paired, while paramagnetic substances have unpaired electrons.

### Step-by-Step Solution:

1. **Identify the Molecules**: We will analyze the following molecules:
- N₂ (Nitrogen)
- O₂ (Oxygen)
- S₂ (Sulfur)
- C₂ (Carbon)

2. **Determine the Total Number of Electrons**:
- **N₂**: Each nitrogen atom has an atomic number of 7, so for N₂, the total number of electrons = 7 + 7 = 14.
- **O₂**: Each oxygen atom has an atomic number of 8, so for O₂, the total number of electrons = 8 + 8 = 16.
- **S₂**: Each sulfur atom has an atomic number of 16, so for S₂, the total number of electrons = 16 + 16 = 32.
- **C₂**: Each carbon atom has an atomic number of 6, so for C₂, the total number of electrons = 6 + 6 = 12.

3. **Write the Electronic Configuration Using Molecular Orbital Theory**:
- **N₂**:
- Configuration: σ1s² σ*1s² σ2s² σ*2s² (2 electrons each in bonding and anti-bonding)
- For 2p: π2p_x¹ π2p_y¹ (1 electron each in bonding)
- Total: 2 unpaired electrons → **Diamagnetic**.
- **O₂**:
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² (2 electrons in bonding)
- For 2p: π2p_x¹ π2p_y¹ (1 electron each in bonding)
- Total: 2 unpaired electrons → **Paramagnetic**.
- **S₂**:
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² (2 electrons in bonding)
- For 2p: π2p_x² π2p_y¹ π2p_z¹ (1 electron each in bonding)
- Total: 2 unpaired electrons → **Paramagnetic**.
- **C₂**:
- Configuration: σ1s² σ*1s² σ2s² σ*2s² (2 electrons in bonding)
- For 2p: π2p_x¹ π2p_y¹ (1 electron each in bonding)
- Total: 0 unpaired electrons → **Diamagnetic**.

4. **Conclusion**:
- The molecules that exhibit diamagnetic behavior are **N₂** and **C₂** since they have all electrons paired.

### Final Answer:
**N₂ and C₂ are expected to exhibit diamagnetic behavior.**