In vapour state, sulphur `(S_2)` shows paramagnetic behaviour due to

Options

A. Presence of one unpaired electron in the antibonding `sigma^**` orbitals
B. Presence of two unpaired electrons in the bonding pi orbitals
C. Presence of one unpaired electrons in the bonding `pi^**` orbitals
D. Presence of two unpaired electrons in the bonding `pi^**` orbitals

Answer

To solve the question regarding the paramagnetic behavior of sulfur in its vapor state, we need to analyze the electronic configuration of the sulfur molecule \( S_2 \) and understand the concept of paramagnetism.

### Step-by-Step Solution:

1. **Understanding the Molecular Structure of \( S_2 \)**:
- Sulfur in its vapor state exists as a diatomic molecule \( S_2 \).

2. **Electronic Configuration**:
- To determine the magnetic properties, we need to look at the molecular orbital (MO) theory. The molecular orbitals are formed by the combination of atomic orbitals from the two sulfur atoms.
- The electronic configuration of \( S_2 \) can be derived from the atomic configuration of sulfur, which is \( [Ne] 3s^2 3p^4 \).

3. **Filling the Molecular Orbitals**:
- For \( S_2 \), the molecular orbitals are filled in the order of increasing energy:
- \( \sigma_{1s}^2 \)
- \( \sigma_{1s}^* \)
- \( \sigma_{2s}^2 \)
- \( \sigma_{2s}^* \)
- \( \sigma_{2p_z}^2 \)
- \( \pi_{2p_x}^2 \)
- \( \pi_{2p_y}^2 \)
- \( \pi_{2p_x}^* \)
- \( \pi_{2p_y}^* \)

4. **Identifying Unpaired Electrons**:
- In the case of \( S_2 \), the two unpaired electrons are located in the \( \pi_{2p_x}^* \) and \( \pi_{2p_y}^* \) molecular orbitals.
- This configuration leads to the presence of two unpaired electrons.

5. **Conclusion on Paramagnetism**:
- The presence of unpaired electrons is the key factor that leads to paramagnetic behavior. Since \( S_2 \) has two unpaired electrons in the antibonding \( \pi \) orbitals, it exhibits paramagnetism in the vapor state.

### Final Answer:
In vapor state, sulfur \( (S_2) \) shows paramagnetic behavior due to the presence of two unpaired electrons in the \( \pi_{2p}^* \) molecular orbitals.

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