Which among the following compounds is paramagnetic ?

Options

A. `KO_(2)`
B. `K_(2)O_(2)`
C. `K_(2)O`
D. `NO_(2)`

Explanation

To determine which among the given compounds is paramagnetic, we need to analyze each option based on the presence of unpaired electrons. A compound is considered paramagnetic if it has one or more unpaired electrons in its electron configuration.

### Step-by-Step Solution:

1. **Understanding Paramagnetism**:
- Paramagnetic substances have unpaired electrons, which contribute to their magnetic properties. In contrast, diamagnetic substances have all electrons paired and do not exhibit magnetism.

2. **Analyzing Compound KO2 (Potassium Superoxide)**:
- Upon dissociation, KO2 gives K⁺ and O2⁻.
- The O2⁻ ion is a superoxide ion. The electron configuration for O2⁻ is:
- σ1s² σ1s² σ2s² σ2s² σ2pz² π2px² π2py² π*2px² π*2py¹
- This configuration shows one unpaired electron in the π*2py orbital, indicating that KO2 is **paramagnetic**.

3. **Analyzing Compound K2O2 (Potassium Peroxide)**:
- Upon dissociation, K2O2 gives 2K⁺ and O2²⁻.
- The O2²⁻ ion is a peroxide ion. The electron configuration for O2²⁻ is:
- σ1s² σ1s² σ2s² σ2s² σ2pz² π2px² π2py²
- All electrons are paired in this configuration, indicating that K2O2 is **diamagnetic**.

4. **Analyzing Compound K2O (Potassium Oxide)**:
- Upon dissociation, K2O gives 2K⁺ and O²⁻.
- The O²⁻ ion is a normal oxide. The electron configuration for O²⁻ is:
- σ1s² σ1s² σ2s² σ2s² σ2pz²
- Again, all electrons are paired, indicating that K2O is **diamagnetic**.

5. **Analyzing Compound NO2 (Nitrogen Dioxide)**:
- NO2 exists as a monomeric structure with one nitrogen atom bonded to two oxygen atoms.
- The nitrogen atom has one unpaired electron in its configuration:
- This gives it a paramagnetic nature due to the presence of the unpaired electron.

### Conclusion:
- The compounds that are paramagnetic are **KO2 (Potassium Superoxide)** and **NO2 (Nitrogen Dioxide)**.
- Therefore, the correct answers are **Option A (KO2)** and **Option D (NO2)**.