Which of the following is diamagnetic ?

Options

A. `O_(2)^(+)`
B. `O_(2)`
C. `O_(2)^(-)`
D. `O_(2)^(2-)`

Answer

To determine which of the given options is diamagnetic, we need to analyze the electronic configurations of the molecules in question. A molecule is considered diamagnetic if it has no unpaired electrons in its electronic configuration. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Diamagnetism and Paramagnetism
- **Diamagnetic**: A substance that has all its electrons paired. It is not attracted to a magnetic field.
- **Paramagnetic**: A substance that has one or more unpaired electrons. It is attracted to a magnetic field.

### Step 2: Identify the Given Molecules
Assuming the options provided are O2+, O2, O2−, and O2²−, we will analyze each one.

### Step 3: Calculate the Total Number of Electrons
1. **O2+**:
- O2 has 16 electrons (8 from each oxygen atom).
- O2+ has 15 electrons (16 - 1 for the positive charge).

2. **O2**:
- O2 has 16 electrons.

3. **O2−**:
- O2 has 16 electrons.
- O2− has 17 electrons (16 + 1 for the negative charge).

4. **O2²−**:
- O2 has 16 electrons.
- O2²− has 18 electrons (16 + 2 for the two negative charges).

### Step 4: Determine the Electronic Configuration
Using Molecular Orbital Theory, we fill the electrons in the molecular orbitals:

1. **O2+ (15 electrons)**:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x² π2p y¹
- Unpaired Electrons: 1 (π2p x or π2p y)
- **Conclusion**: Paramagnetic

2. **O2 (16 electrons)**:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x² π2p y²
- Unpaired Electrons: 0
- **Conclusion**: Diamagnetic

3. **O2− (17 electrons)**:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x² π2p y² π2p x¹
- Unpaired Electrons: 1 (π2p x)
- **Conclusion**: Paramagnetic

4. **O2²− (18 electrons)**:
- Configuration: σ1s² σ1s*² σ2s² σ2s*² σ2p z² π2p x² π2p y² π2p x²
- Unpaired Electrons: 0
- **Conclusion**: Diamagnetic

### Step 5: Identify the Diamagnetic Species
From the analysis:
- O2 is diamagnetic.
- O2²− is also diamagnetic.

### Final Answer
The diamagnetic species among the options is **O2²−**.