The number of unpaired electrons in `O_(2)` molecule is

Options

A. zero
B. 1
C. 2
D. 3

Answer

To determine the number of unpaired electrons in the O₂ molecule, we can follow these steps:

### Step 1: Determine the Total Number of Electrons
The O₂ molecule consists of two oxygen atoms. Each oxygen atom has 8 electrons, so the total number of electrons in O₂ is:
\[ 2 \times 8 = 16 \text{ electrons} \]

### Step 2: Write the Molecular Orbital Configuration
We will fill the molecular orbitals in order of increasing energy. The order of filling for the molecular orbitals for O₂ is as follows:
- σ(1s)
- σ*(1s)
- σ(2s)
- σ*(2s)
- σ(2p_z)
- π(2p_x) = π(2p_y)
- π*(2p_x) = π*(2p_y)

Now we fill these orbitals with the 16 electrons:
1. σ(1s)²
2. σ*(1s)²
3. σ(2s)²
4. σ*(2s)²
5. σ(2p_z)²
6. π(2p_x)²
7. π(2p_y)²
8. π*(2p_x)¹
9. π*(2p_y)¹

### Step 3: Count the Unpaired Electrons
From the molecular orbital configuration:
- σ(1s)²: 2 paired electrons
- σ*(1s)²: 2 paired electrons
- σ(2s)²: 2 paired electrons
- σ*(2s)²: 2 paired electrons
- σ(2p_z)²: 2 paired electrons
- π(2p_x)²: 2 paired electrons
- π(2p_y)²: 2 paired electrons
- π*(2p_x)¹: 1 unpaired electron
- π*(2p_y)¹: 1 unpaired electron

Thus, the number of unpaired electrons in O₂ is:
\[ 1 + 1 = 2 \text{ unpaired electrons} \]

### Conclusion
The number of unpaired electrons in the O₂ molecule is 2.

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