Which of the following species is paramagnetic in nature?

Options

A. Carbonium ion
B. Free radical
C. Singlet Carbene
D. Nitrene

Answer

To determine which species is paramagnetic in nature, we need to identify the species that has unpaired electrons. Let's analyze the options step by step.

### Step 1: Understand the concept of paramagnetism
- Paramagnetic species have unpaired electrons, while diamagnetic species have all electrons paired.

### Step 2: Analyze the first species - Carbonium ion
- A carbonium ion (R-C^+) has a positive charge and typically has six electrons.
- In this case, all electrons are paired.
- **Conclusion**: The carbonium ion is **diamagnetic**.

### Step 3: Analyze the second species - Free radical (e.g., CH3 radical)
- A free radical like CH3 has seven electrons.
- In this structure, one electron is unpaired.
- **Conclusion**: The CH3 radical is **paramagnetic**.

### Step 4: Analyze the third species - Singlet carbene
- A singlet carbene has two electrons in its bonding orbitals and one vacant orbital.
- All electrons are paired in this configuration.
- **Conclusion**: The singlet carbene is **diamagnetic**.

### Step 5: Analyze the fourth species - Nitrene
- An alkyl nitrene has five valence electrons from nitrogen.
- In its structure, there are four paired electrons and one unpaired electron.
- **Conclusion**: The nitrene is **paramagnetic**.

### Final Conclusion
Among the species analyzed, the **free radical (CH3 radical)** is paramagnetic due to the presence of unpaired electrons.

### Summary of Results
1. Carbonium ion - Diamagnetic
2. Free radical (CH3) - Paramagnetic
3. Singlet carbene - Diamagnetic
4. Nitrene - Paramagnetic

Thus, the correct answer is that the **free radical (CH3)** is paramagnetic.

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