Due to the presence of an unpaired electron, free radicals are

Options

A. cations
B. anions
C. chemically inactive
D. chemically reactive.

Explanation

### Step-by-Step Solution:

1. **Understanding Free Radicals**:
- A free radical is a chemical species that has one or more unpaired electrons. This unpaired electron makes the species highly reactive.

2. **Identifying the Characteristics of Free Radicals**:
- Free radicals are typically neutral species, meaning they do not carry a net charge. However, due to the presence of the unpaired electron, they are unstable and seek to pair this electron.

3. **Example of a Free Radical**:
- Consider the methyl radical (CH3•). In this case, the carbon atom in the methyl group has three hydrogen atoms and one unpaired electron, making it a free radical.

4. **Reactivity of Free Radicals**:
- Free radicals are known to be chemically reactive. They can participate in various reactions, including chain reactions, where they can react with other molecules to form stable products.

5. **Conclusion**:
- Therefore, due to the presence of an unpaired electron, free radicals are chemically reactive species. They actively seek to pair their unpaired electrons by reacting with other molecules.

### Final Answer:
Free radicals are chemically reactive due to the presence of an unpaired electron.

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