Which of the following species exhibits the diamagnetic behaviour?

Options

A. `O_(2)^(2-)`
B. ` O_(2)^(+)`
C. `O_(2)`
D. `NO.`

Explanation

To determine which of the given species exhibits diamagnetic behavior, we need to analyze the electron configurations of the species in question using molecular orbital theory. Here’s a step-by-step solution:

### Step 1: Understand Diamagnetism and Paramagnetism
Diamagnetic substances are those that do not have unpaired electrons and are not attracted to a magnetic field. Paramagnetic substances have one or more unpaired electrons and are attracted to a magnetic field.

### Step 2: Identify the Species
Let's consider the species mentioned in the question: O2, O2^2-, and O2^+.

### Step 3: Determine the Electron Configuration of O2
The molecular orbital configuration for O2 (oxygen molecule) is:
- Total electrons: 16 (8 from each oxygen atom)
- Configuration: (σ1s)² (σ*1s)² (σ2s)² (σ*2s)² (σ2p_z)² (π2p_x)² (π2p_y)² (π*2p_x)¹ (π*2p_y)¹
- O2 has two unpaired electrons in the π*2p orbitals, making it paramagnetic.

### Step 4: Determine the Electron Configuration of O2^2-
For O2^2- (the superoxide ion), we add two electrons to the O2 configuration:
- Configuration: (σ1s)² (σ*1s)² (σ2s)² (σ*2s)² (σ2p_z)² (π2p_x)² (π2p_y)² (π*2p_x)² (π*2p_y)²
- O2^2- has all electrons paired, making it diamagnetic.

### Step 5: Determine the Electron Configuration of O2^+
For O2^+ (the oxygen cation), we remove one electron from the O2 configuration:
- Configuration: (σ1s)² (σ*1s)² (σ2s)² (σ*2s)² (σ2p_z)² (π2p_x)² (π2p_y)² (π*2p_x)¹ (π*2p_y)²
- O2^+ has one unpaired electron in the π*2p_x orbital, making it paramagnetic.

### Step 6: Conclusion
From the analysis:
- O2 is paramagnetic.
- O2^2- is diamagnetic.
- O2^+ is paramagnetic.

Thus, the species that exhibits diamagnetic behavior is **O2^2-**.

### Summary of Steps:
1. Understand the concepts of diamagnetism and paramagnetism.
2. Identify the species in question.
3. Determine the electron configuration of O2.
4. Determine the electron configuration of O2^2-.
5. Determine the electron configuration of O2^+.
6. Conclude which species is diamagnetic.