During change of `O_(2)` to `O_(2)^(2-)` ion, the electrons add on which of the following orbitals ?

Options

A. `pi^(**)` orbital
B. `pi`orbital
C. `sigma^(**)` orbital
D. `sigma` orbital.

Explanation

To determine the orbital in which electrons are added during the conversion of \( O_2 \) to \( O_2^{2-} \), we will analyze the molecular orbital (MO) configuration of both species.

### Step-by-Step Solution:

1. **Identify the Total Electrons in \( O_2 \)**:
- Oxygen has an atomic number of 8, so \( O_2 \) has a total of \( 2 \times 8 = 16 \) electrons.

2. **Write the Molecular Orbital Configuration for \( O_2 \)**:
- The molecular orbital configuration for \( O_2 \) is:
\[ \sigma_{1s}^2 \sigma^*_{1s}^2 \sigma_{2s}^2 \sigma^*_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^*_{2p_x}^1 \pi^*_{2p_y}^1 \]
- This can be simplified to:
\[ \sigma_{1s}^2 \sigma^*_{1s}^2 \sigma_{2s}^2 \sigma^*_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^*_{2p}^2 \]

3. **Determine the Total Electrons in \( O_2^{2-} \)**:
- The \( O_2^{2-} \) ion has 2 additional electrons compared to \( O_2 \), giving it a total of \( 16 + 2 = 18 \) electrons.

4. **Add the Electrons to the Molecular Orbital Configuration**:
- The additional electrons will occupy the next available molecular orbital, which is the \( \pi^* \) orbital.
- Therefore, the configuration for \( O_2^{2-} \) will be:
\[ \sigma_{1s}^2 \sigma^*_{1s}^2 \sigma_{2s}^2 \sigma^*_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^*_{2p_x}^2 \pi^*_{2p_y}^2 \]

5. **Conclusion**:
- The electrons are added to the \( \pi^* \) orbitals during the formation of the \( O_2^{2-} \) ion.

### Final Answer:
The electrons add to the \( \pi^* \) orbitals.