Which of the following species is paramagnetic ? .

Options

A. `CO_(2)`
B. `O_(2)^(2-)`
C. `CN^(Theta)`
D. `NO`

Explanation

To determine which of the given species is paramagnetic, we need to analyze each option for the presence of unpaired electrons. A species is considered paramagnetic if it has at least one unpaired electron.

### Step-by-Step Solution:

1. **Identify the Species**: We have four species to analyze: CO2, O2^2-, CN^-, and NO.

2. **Analyze CO2**:
- The electronic configuration of CO2 can be derived from its molecular orbital diagram.
- In CO2, all electrons are paired.
- **Conclusion**: CO2 is **diamagnetic** (no unpaired electrons).

3. **Analyze O2^2- (Peroxide Ion)**:
- The electronic configuration of O2^2- is as follows:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_x², π2p_y², π2p_z², π*2p_y², π*2p_z².
- All electrons in this configuration are paired.
- **Conclusion**: O2^2- is **diamagnetic** (no unpaired electrons).

4. **Analyze CN^- (Cyanide Ion)**:
- The electronic configuration of CN^- is:
- σ1s², σ*1s², σ2s², σ*2s², π2p_y², π2p_z², σ2p_x².
- All electrons are paired in this configuration.
- **Conclusion**: CN^- is **diamagnetic** (no unpaired electrons).

5. **Analyze NO (Nitric Oxide)**:
- The electronic configuration of NO is:
- σ1s², σ*1s², σ2s², σ*2s², σ2p_x², π2p_y², π2p_z², π*2p_y¹, π*2p_z⁰.
- Here, we see that there is one unpaired electron in the π*2p_y orbital.
- **Conclusion**: NO is **paramagnetic** (has unpaired electron).

### Final Answer:
The species that is paramagnetic is **NO**.