Which of the following species not paramagnetic ?

Options

A. `CO`
B. `O_2`
C. `B_2`
D. `NO`

Answer

To determine which of the following species is not paramagnetic, we need to analyze the electronic configurations of each species and identify the presence of unpaired electrons. A species is considered paramagnetic if it has unpaired electrons, while it is diamagnetic if all electrons are paired.

### Step-by-Step Solution:

1. **Identify the Species**: We need to analyze the electronic configurations of the given species. The species mentioned in the video are CO (carbon monoxide) and O2 (dioxygen).

2. **Molecular Orbital Theory (MOT)**: We will use Molecular Orbital Theory to fill the molecular orbitals with electrons for each species.

3. **Analyze CO (Carbon Monoxide)**:
- CO has a total of 14 electrons (6 from carbon and 8 from oxygen).
- The order of filling the molecular orbitals is:
- σ1s (2), σ1s* (2), σ2s (2), σ2s* (2),
- σ2p_z (2), π2p_x (2), π2p_y (2), π2p_x* (1), π2p_y* (1).
- Filling the orbitals gives us:
- σ1s (2), σ1s* (0), σ2s (2), σ2s* (0),
- σ2p_z (2), π2p_x (2), π2p_y (2), π2p_x* (0), π2p_y* (0).
- All electrons are paired in CO, making it **diamagnetic**.

4. **Analyze O2 (Dioxygen)**:
- O2 has a total of 16 electrons (8 from each oxygen).
- The order of filling the molecular orbitals is the same as above.
- Filling the orbitals gives us:
- σ1s (2), σ1s* (0), σ2s (2), σ2s* (0),
- σ2p_z (2), π2p_x (2), π2p_y (2), π2p_x* (1), π2p_y* (1).
- In O2, there are two unpaired electrons in the π2p_x* and π2p_y* orbitals, making it **paramagnetic**.

5. **Conclusion**: Since CO is the only species that has all paired electrons, it is the species that is **not paramagnetic**.

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