Which of the following molecule species is/are having `pi_(2p)` as H.O.M.O (highest occupied molecular orbital) :

Options

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

Answer

To determine which of the following molecular species has π2p as the highest occupied molecular orbital (HOMO), we need to analyze the molecular orbital electronic configurations of each species.

### Step-by-Step Solution:

1. **Identify the Total Number of Electrons:**
- For each molecular species, calculate the total number of electrons based on the molecular formula and the charge.

2. **Draw the Molecular Orbital Diagram:**
- For each molecule, draw the molecular orbital energy level diagram. The order of filling for molecular orbitals is generally:
- σ1s, σ*1s, σ2s, σ*2s, σ2p_z, π2p_x, π2p_y, π*2p_x, π*2p_y

3. **Fill the Electrons According to the Aufbau Principle:**
- Fill the molecular orbitals with the calculated number of electrons, following Hund's rule and the Pauli exclusion principle.

4. **Determine the HOMO:**
- Identify the highest occupied molecular orbital (HOMO) by looking at the last filled orbital.

5. **Evaluate Each Molecular Species:**
- **N2-**:
- Total electrons = 15
- Configuration: σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x², π2p_y¹
- HOMO = π*2p (not π2p)
- **O2+**:
- Total electrons = 14
- Configuration: σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x¹, π2p_y¹
- HOMO = π2p (correct)
- **NO+**:
- Total electrons = 14
- Configuration: σ1s², σ*1s², σ2s², σ*2s², σ2p_z², π2p_x¹, π2p_y¹
- HOMO = π2p (correct)
- **B2+**:
- Total electrons = 9
- Configuration: σ1s², σ*1s², σ2s², σ*2s², π2p_x¹
- HOMO = π2p (correct)

6. **Conclusion:**
- The molecular species that have π2p as HOMO are O2+, NO+, and B2+. Therefore, the correct options are 2, 3, and 4.

### Final Answer:
The molecular species having π2p as HOMO are:
- O2+
- NO+
- B2+