Which of the following has unpaired electron(s)?

Options

A. `O_(2)^(-)`
B. `N_(2)^(2+)`
C. `O_(2)^(2-)`
D. `N_(2)`

Answer

To determine which of the given molecules has unpaired electrons, we will analyze the electronic configurations of the molecules involved, specifically O2, O2-, and N2, as well as N2 2+. We will utilize molecular orbital theory to find the answer.

### Step-by-Step Solution:

1. **Identify the Total Electrons in Each Molecule:**
- O2 has 16 electrons (8 from each oxygen atom).
- O2- has 17 electrons (16 from O2 + 1 additional electron).
- N2 has 14 electrons (7 from each nitrogen atom).
- N2 2+ has 12 electrons (14 from N2 - 2 electrons).

2. **Write the Molecular Orbital Configuration:**
- For O2:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² (2 electrons each in the bonding and antibonding orbitals)
- Then, for the p orbitals: π2px² = π2py² (2 electrons each) and σ2pz² (2 electrons).
- Total: σ1s² σ1s*² σ2s² σ2s*² π2px² π2py² σ2pz²
- This results in 2 unpaired electrons in the π2px and π2py orbitals.

- For O2-:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² π2px² π2py² σ2pz² (same as O2 but with one additional electron).
- The additional electron will pair up with one of the unpaired electrons in the π orbitals.
- Total: σ1s² σ1s*² σ2s² σ2s*² π2px² π2py² σ2pz²
- This results in no unpaired electrons.

- For N2:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² π2px² π2py² σ2pz²
- All electrons are paired.

- For N2 2+:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² π2px² π2py²
- Removing 2 electrons from the outermost orbitals (which are π orbitals) results in all electrons being paired.

3. **Conclusion:**
- O2 has unpaired electrons.
- O2- has no unpaired electrons.
- N2 has no unpaired electrons.
- N2 2+ has no unpaired electrons.

Thus, the only molecule with unpaired electrons is **O2**.

### Final Answer:
The molecule that has unpaired electron(s) is **O2**.