Which one of the following pairs consists of only paramagnetic species

Options

A. `O_2, NO`
B. `O_2^(+)`,`O_2^(2-)`
C. `CO, NO`
D. `NO, NO^(+)`

Explanation

To determine which pair consists of only paramagnetic species, we need to analyze the electronic configurations of the given molecules. Let's go through the options step by step.

### Step 1: Analyze the first option - O2 and NO
1. **O2 (Oxygen molecule)**:
- Total electrons: 16 (8 from each O atom).
- Molecular orbital configuration:
- σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x¹ π*2p_y¹
- Unpaired electrons: 2 (in π*2p_x and π*2p_y).
- Conclusion: O2 is paramagnetic.

2. **NO (Nitric oxide)**:
- Total electrons: 15 (7 from N and 8 from O).
- Molecular orbital configuration:
- Similar to O2 but with one less electron.
- Unpaired electrons: 1.
- Conclusion: NO is paramagnetic.

**Result**: Both O2 and NO are paramagnetic.

### Step 2: Analyze the second option - O2⁺ and O2²⁻
1. **O2⁺**:
- Total electrons: 15 (16 from O2 minus 1).
- Unpaired electrons: 1 (in π*2p_x).
- Conclusion: O2⁺ is paramagnetic.

2. **O2²⁻**:
- Total electrons: 18 (16 from O2 plus 2).
- Unpaired electrons: 0 (all electrons are paired).
- Conclusion: O2²⁻ is diamagnetic.

**Result**: O2⁺ is paramagnetic, but O2²⁻ is diamagnetic.

### Step 3: Analyze the third option - CO and NO
1. **CO (Carbon monoxide)**:
- Total electrons: 14 (6 from C and 8 from O).
- Unpaired electrons: 0 (all electrons are paired).
- Conclusion: CO is diamagnetic.

2. **NO (Nitric oxide)**:
- Already established as paramagnetic.

**Result**: CO is diamagnetic, while NO is paramagnetic.

### Step 4: Analyze the fourth option - NO and NO⁺
1. **NO**:
- Already established as paramagnetic.

2. **NO⁺**:
- Total electrons: 14 (15 from NO minus 1).
- Unpaired electrons: 0 (all electrons are paired).
- Conclusion: NO⁺ is diamagnetic.

**Result**: NO is paramagnetic, but NO⁺ is diamagnetic.

### Step 5: Analyze the fifth option - O2 and N2⁻
1. **O2**:
- Already established as paramagnetic.

2. **N2⁻**:
- Total electrons: 15 (14 from N2 plus 1).
- Unpaired electrons: 1.
- Conclusion: N2⁻ is paramagnetic.

**Result**: Both O2 and N2⁻ are paramagnetic.

### Final Conclusion:
The pairs that consist of only paramagnetic species are:
- **First option: O2 and NO**
- **Fifth option: O2 and N2⁻**