Paramagnetic behaviour of `KO_2` is due to the fact that unpaired electron is present in

Options

A. `pi2p` molecular orbital
B. `pi*2p` molecular orbital
C. `sigma 2p` molecular orbital
D. `sigma*2p` molecular orbital

Answer

To determine the paramagnetic behavior of potassium superoxide (KO₂) and identify the presence of unpaired electrons, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding KO₂**:
- KO₂ is composed of potassium (K) and superoxide ion (O₂⁻). The potassium ion (K⁺) does not contribute to the paramagnetic behavior since it has a complete electron configuration.

2. **Analyzing the Superoxide Ion (O₂⁻)**:
- The superoxide ion (O₂⁻) has a total of 10 electrons. This is because the molecular oxygen (O₂) has 16 electrons (8 from each oxygen atom), and the addition of 2 electrons (due to the -1 charge) gives us 18 electrons in total. However, we only consider the relevant molecular orbitals for O₂⁻.

3. **Molecular Orbital Configuration**:
- The molecular orbital configuration for O₂⁻ can be written as:
- σ1s² σ*1s² σ2s² σ*2s² σ2p_z² (bonding)
- π2p_x² π2p_y² (bonding)
- π*2p_x² π*2p_y¹ (antibonding)
- Here, the π*2p_x and π*2p_y orbitals are the antibonding orbitals.

4. **Identifying Unpaired Electrons**:
- In the configuration above, we see that the π*2p_x orbital has 2 electrons and the π*2p_y orbital has 1 unpaired electron. This unpaired electron is responsible for the paramagnetic behavior of KO₂.

5. **Conclusion**:
- The presence of the unpaired electron in the π*2p molecular orbital leads to the paramagnetic behavior of KO₂.

### Final Answer:
The unpaired electron in KO₂ is present in the **π*2p molecular orbital**.

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