Assuming `2s-2p` mixing is `NOT` operative, the paramagnetic species among the following is .

Options

A. `Be_(2)`
B. `B_(2)`
C. `C_(2)`
D. `N_(2)`

Explanation

To determine the paramagnetic species among the given options (BE2, B2, C2, N2) assuming that 2s-2p mixing is not operative, we will follow these steps:

### Step 1: Understand the Molecular Orbital (MO) Theory
In the absence of 2s-2p mixing, the order of molecular orbitals for diatomic molecules is:
- σ1s
- σ*1s
- σ2s
- σ*2s
- σ2pz
- π2px = π2py (degenerate)
- π*2px = π*2py (degenerate)
- σ*2pz

### Step 2: Determine the Total Number of Electrons for Each Species
- **BE2**: Beryllium has 4 electrons, so BE2 has a total of 8 electrons.
- **B2**: Boron has 5 electrons, so B2 has a total of 10 electrons.
- **C2**: Carbon has 6 electrons, so C2 has a total of 12 electrons.
- **N2**: Nitrogen has 7 electrons, so N2 has a total of 14 electrons.

### Step 3: Fill the Molecular Orbitals for Each Species
1. **BE2 (8 electrons)**:
- Fill: σ1s², σ*1s², σ2s², σ*2s²
- Result: All electrons are paired. **(Diamagnetic)**

2. **B2 (10 electrons)**:
- Fill: σ1s², σ*1s², σ2s², σ*2s², σ2pz²
- Result: All electrons are paired. **(Diamagnetic)**

3. **C2 (12 electrons)**:
- Fill: σ1s², σ*1s², σ2s², σ*2s², σ2pz², π2px¹, π2py¹
- Result: There are unpaired electrons in π2px and π2py. **(Paramagnetic)**

4. **N2 (14 electrons)**:
- Fill: σ1s², σ*1s², σ2s², σ*2s², σ2pz², π2px², π2py²
- Result: All electrons are paired. **(Diamagnetic)**

### Step 4: Conclusion
The only species that is paramagnetic due to the presence of unpaired electrons is **C2**.

### Final Answer
**C2 is the paramagnetic species.**

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