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 molecular orbital containing the unpaired electron, we can follow these steps:

### Step 1: Understand the Composition of KO₂
KO₂ is composed of potassium (K) and the superoxide ion (O₂⁻). When KO₂ dissociates, it forms K⁺ and O₂⁻ ions.

### Step 2: Determine the Electron Count for O₂⁻
The superoxide ion (O₂⁻) has a total of 17 electrons. This is calculated as follows:
- Each oxygen atom contributes 8 electrons (2 oxygen atoms = 16 electrons).
- The additional negative charge (−1) from the superoxide ion adds one more electron, resulting in a total of 17 electrons.

### Step 3: Write the Molecular Orbital Configuration for O₂⁻
Using molecular orbital theory, we can fill the molecular orbitals with the 17 electrons. The order of filling for O₂⁻ is as follows:
1. σ1s²
2. σ*1s²
3. σ2s²
4. σ*2s²
5. σ2p²
6. π2p² (which consists of π2p_x² and π2p_y²)
7. π*2p¹ (which consists of π*2p_x¹ and π*2p_y⁰)

The molecular orbital configuration for O₂⁻ can be summarized as:
- σ1s², σ*1s², σ2s², σ*2s², σ2p², π2p², π*2p¹

### Step 4: Identify the Unpaired Electron
From the molecular orbital configuration, we observe that the π*2p molecular orbital contains one unpaired electron. This unpaired electron is responsible for the paramagnetic behavior of KO₂.

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

### Final Answer
The correct option is: **π*2p molecular orbital (Option 2)**.

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