Smallest intermolecular distance is found in

Options

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

Explanation

To determine which species has the smallest intermolecular distance, we can analyze the bond orders of the given options. The bond order is inversely related to the bond length; thus, a higher bond order indicates a shorter bond length (or smaller intermolecular distance).

Here are the steps to solve the problem:

### Step 1: Identify the species and their molecular orbital configurations
The species given in the question are:
1. O2 (molecular oxygen)
2. O2^2+ (dioxygen dication)
3. O2^- (dioxygen anion)
4. O2^2- (dioxygen dianion)

### Step 2: Calculate the bond order for each species
The bond order can be calculated using the formula:
\[ \text{Bond Order} = \frac{(\text{Number of electrons in bonding orbitals}) - (\text{Number of electrons in antibonding orbitals})}{2} \]

#### For O2:
- Bonding electrons: 10 (2 in σ1s, 2 in σ*1s, 2 in σ2s, 2 in σ*2s, 2 in π2p)
- Antibonding electrons: 6 (2 in π*2p)
- Bond Order: \( \frac{10 - 6}{2} = 2 \)

#### For O2^2+:
- Electrons in antibonding orbitals decrease by 2 (due to losing 2 electrons).
- Bond Order: \( \frac{10 - 4}{2} = 3 \)

#### For O2^-:
- Add 1 electron to antibonding orbitals.
- Bond Order: \( \frac{10 - 7}{2} = 1.5 \)

#### For O2^2-:
- Add 2 electrons to antibonding orbitals.
- Bond Order: \( \frac{10 - 8}{2} = 1 \)

### Step 3: Compare the bond orders
- O2: Bond Order = 2
- O2^2+: Bond Order = 3
- O2^-: Bond Order = 1.5
- O2^2-: Bond Order = 1

### Step 4: Determine the smallest intermolecular distance
Since bond order is inversely proportional to bond length, the species with the highest bond order will have the smallest intermolecular distance.

From our calculations:
- O2^2+ has the highest bond order of 3.

### Conclusion
Therefore, the species with the smallest intermolecular distance is **O2^2+**.