Bond order increases in which of the given transitions ?

Options

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

Answer

To determine in which of the given transitions the bond order increases, we will analyze each transition step by step.

### Step 1: Analyze the transition from CO to CO⁺
1. **Molecular Orbital (MO) Configuration of CO**:
- Carbon (C): 1s² 2s² 2p²
- Oxygen (O): 1s² 2s² 2p⁴
- Total electrons in CO: 10 (6 bonding, 0 antibonding)
- Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2 = (6 - 0) / 2 = 3

2. **Molecular Orbital (MO) Configuration of CO⁺**:
- CO⁺ has one less electron, so it has 9 electrons.
- Bond order = (5 - 0) / 2 = 2.5

**Conclusion**: Bond order decreases from 3 to 2.5.

### Step 2: Analyze the transition from N₂ to N₂⁻
1. **Molecular Orbital (MO) Configuration of N₂**:
- Nitrogen (N): 1s² 2s² 2p³
- Total electrons in N₂: 14 (6 bonding, 0 antibonding)
- Bond order = (6 - 0) / 2 = 3

2. **Molecular Orbital (MO) Configuration of N₂⁻**:
- N₂⁻ has one extra electron, so it has 15 electrons.
- Bond order = (6 - 1) / 2 = 2.5

**Conclusion**: Bond order decreases from 3 to 2.5.

### Step 3: Analyze the transition from O₂ to O₂⁺
1. **Molecular Orbital (MO) Configuration of O₂**:
- Oxygen (O): 1s² 2s² 2p⁴
- Total electrons in O₂: 16 (6 bonding, 2 antibonding)
- Bond order = (6 - 2) / 2 = 2

2. **Molecular Orbital (MO) Configuration of O₂⁺**:
- O₂⁺ has one less electron, so it has 15 electrons.
- Bond order = (6 - 1) / 2 = 2.5

**Conclusion**: Bond order increases from 2 to 2.5.

### Step 4: Analyze the transition from O₂ to O₂²⁻
1. **Molecular Orbital (MO) Configuration of O₂**:
- Total electrons in O₂: 16 (6 bonding, 2 antibonding)
- Bond order = (6 - 2) / 2 = 2

2. **Molecular Orbital (MO) Configuration of O₂²⁻**:
- O₂²⁻ has two extra electrons, so it has 18 electrons.
- Bond order = (6 - 4) / 2 = 1

**Conclusion**: Bond order decreases from 2 to 1.

### Final Conclusion:
- The only transition where the bond order increases is from O₂ to O₂⁺ (from 2 to 2.5).