Which of the following is a paramagnetic compound ?

Options

A. `KO_2`
B. `SiO_2`
C. `TiO_2`
D. `BaO_2`

Answer

To determine which of the given compounds is paramagnetic, we need to analyze the electronic configurations of each compound and check for the presence of unpaired electrons. A compound is considered paramagnetic if it has at least one unpaired electron.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds provided are:
- KO2 (Potassium superoxide)
- SiO2 (Silicon dioxide)
- TiO2 (Titanium dioxide)

2. **Check KO2**:
- **Oxidation State**: In KO2, potassium (K) has an oxidation state of +1, and the superoxide ion (O2^-) has an overall charge of -1.
- **Electron Count**: The superoxide ion (O2^-) has 17 electrons (8 from each oxygen atom and 1 extra due to the negative charge).
- **Molecular Orbital Configuration**:
- The configuration for O2^- is:
- σ1s² σ*1s² σ2s² σ*2s² σ2p_z² π2p_x² π2p_y² π*2p_x¹
- In this configuration, there is one unpaired electron in the π*2p_x orbital.
- **Conclusion**: KO2 is paramagnetic because it has unpaired electrons.

3. **Check SiO2**:
- **Oxidation State**: Silicon (Si) has an oxidation state of +4, and each oxygen (O) has an oxidation state of -2.
- **Electron Count**: SiO2 has a total of 18 electrons (14 from Si and 8 from two O atoms).
- **Molecular Orbital Configuration**:
- The configuration for SiO2 is fully filled, meaning all electrons are paired.
- **Conclusion**: SiO2 is diamagnetic because it has no unpaired electrons.

4. **Check TiO2**:
- **Oxidation State**: Titanium (Ti) has an oxidation state of +4, and each oxygen (O) has an oxidation state of -2.
- **Electron Count**: TiO2 has a total of 22 electrons (22 from Ti and O).
- **Molecular Orbital Configuration**:
- The configuration for TiO2 is also fully filled, meaning all electrons are paired.
- **Conclusion**: TiO2 is diamagnetic because it has no unpaired electrons.

5. **Final Conclusion**: Among the given options, only KO2 is paramagnetic due to the presence of unpaired electrons.

### Summary:
- **Paramagnetic Compound**: KO2
- **Diamagnetic Compounds**: SiO2 and TiO2