Which species does not exhibit paramagnetism ?

Options

A. `N_(2)^(+)`
B. `O_(2)^(-)`
C. CO
D. NO

Answer

To determine which species does not exhibit paramagnetism, we need to analyze the electronic configurations of the given species and identify the presence of unpaired electrons. Paramagnetic species have unpaired electrons, while diamagnetic species have all paired electrons.

### Step-by-step Solution:

1. **Understanding Paramagnetism**:
- Paramagnetic substances contain unpaired electrons and are attracted to magnetic fields.
- Diamagnetic substances have all electrons paired and are not attracted to magnetic fields.

2. **Analyzing N2+**:
- N2 has 14 electrons. N2+ has 13 electrons (one less).
- Electronic configuration of N2+:
- σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x¹ π2p y¹
- There are unpaired electrons in the π2p x and π2p y orbitals, indicating that N2+ is **paramagnetic**.

3. **Analyzing O2-**:
- O2 has 16 electrons. O2- has 17 electrons (one more).
- Electronic configuration of O2-:
- σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x² π2p y² π2p x¹ π2p y¹
- There is one unpaired electron in the π2p x and π2p y orbitals, indicating that O2- is **paramagnetic**.

4. **Analyzing NO**:
- NO has a total of 11 electrons.
- Electronic configuration of NO:
- σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x¹
- There is one unpaired electron in the π2p x orbital, indicating that NO is **paramagnetic**.

5. **Analyzing CO**:
- CO has a total of 10 electrons.
- Electronic configuration of CO:
- σ1s² σ1s*² σ2s² σ2s*² σ2p z²
- All electrons are paired, indicating that CO is **diamagnetic**.

6. **Conclusion**:
- Among the species analyzed, CO is the only species that does not exhibit paramagnetism as it has all paired electrons.

### Final Answer:
The species that does not exhibit paramagnetism is **CO (Carbon Monoxide)**.