Which of the following is an odd electron molecule?

Options

A. `CO_2`
B. `SO_2`
C. `NO_2`
D. `AL_2O_3`

Answer

To determine which of the given molecules is an odd electron molecule, we need to analyze the number of valence electrons in each molecule and see if any of them have an unpaired electron.

### Step-by-Step Solution:

1. **Understanding Odd Electron Molecules**:
- An odd electron molecule is one that has an unpaired electron in its structure. This occurs when the total number of valence electrons is odd.

2. **Analyzing Carbon Dioxide (CO2)**:
- Carbon (C) has 4 valence electrons and Oxygen (O) has 6 valence electrons.
- Total valence electrons in CO2 = 4 (from C) + 6 (from O) + 6 (from O) = 16 electrons.
- 16 is an even number, and all electrons can be paired in bonds and lone pairs. Therefore, CO2 does not have an odd electron.

3. **Analyzing Sulfur Dioxide (SO2)**:
- Sulfur (S) has 6 valence electrons and Oxygen (O) has 6 valence electrons.
- Total valence electrons in SO2 = 6 (from S) + 6 (from O) + 6 (from O) = 18 electrons.
- 18 is also an even number, and all electrons can be paired. Thus, SO2 does not have an odd electron.

4. **Analyzing Nitric Oxide (NO)**:
- Nitrogen (N) has 5 valence electrons and Oxygen (O) has 6 valence electrons.
- Total valence electrons in NO = 5 (from N) + 6 (from O) = 11 electrons.
- 11 is an odd number, which means there will be one unpaired electron. Therefore, NO is an odd electron molecule.

5. **Analyzing Aluminum Oxide (Al2O3)**:
- Aluminum (Al) has 3 valence electrons and Oxygen (O) has 6 valence electrons.
- Total valence electrons in Al2O3 = 2(3) (from Al) + 3(6) (from O) = 6 + 18 = 24 electrons.
- 24 is an even number, and all electrons can be paired. Thus, Al2O3 does not have an odd electron.

### Conclusion:
Among the given options, the only odd electron molecule is **NO (Nitric Oxide)**.