Which of the following chemical species is most stable?

Options

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

Answer

To determine which of the given chemical species (O2, O2+, O2-, O2^2-) is the most stable, we will calculate the bond order for each species. The bond order is a measure of the stability of a chemical bond, with higher bond orders indicating greater stability.

### Step-by-Step Solution:

1. **Identify the Number of Electrons:**
- O2: 16 electrons
- O2+: 15 electrons (one electron removed)
- O2-: 17 electrons (one electron added)
- O2^2-: 18 electrons (two electrons added)

2. **Molecular Orbital Configuration:**
- For O2 (16 electrons):
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x²
- For O2+ (15 electrons):
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x¹
- For O2- (17 electrons):
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x² π*2p_y¹
- For O2^2- (18 electrons):
- Configuration: σ1s² σ*1s² σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x² π*2p_y²

3. **Calculate Bond Order:**
- **Bond Order Formula:**
\[ \text{Bond Order} = \frac{1}{2} \times (\text{Number of Bonding Electrons} - \text{Number of Antibonding Electrons}) \]

- **For O2:**
- Bonding Electrons = 10 (σ1s² + σ2s² + σ2p_z² + π2p_x² + π2p_y²)
- Antibonding Electrons = 6 (σ*1s² + σ*2s² + π*2p_x²)
- Bond Order = \( \frac{1}{2} \times (10 - 6) = 2 \)

- **For O2+:**
- Bonding Electrons = 10
- Antibonding Electrons = 5 (removal of one electron from π*2p_x)
- Bond Order = \( \frac{1}{2} \times (10 - 5) = 2.5 \)

- **For O2-:**
- Bonding Electrons = 10
- Antibonding Electrons = 7 (addition of one electron to π*2p_y)
- Bond Order = \( \frac{1}{2} \times (10 - 7) = 1.5 \)

- **For O2^2-:**
- Bonding Electrons = 10
- Antibonding Electrons = 8 (addition of two electrons to π*2p_y)
- Bond Order = \( \frac{1}{2} \times (10 - 8) = 1 \)

4. **Compare Bond Orders:**
- O2: Bond Order = 2
- O2+: Bond Order = 2.5
- O2-: Bond Order = 1.5
- O2^2-: Bond Order = 1

5. **Conclusion:**
- The species with the highest bond order is O2+, which has a bond order of 2.5. Therefore, O2+ is the most stable species among the options provided.

### Final Answer:
**O2+ is the most stable chemical species.**