What is the bond order of `O_2` molecule ?

Explanation

To find the bond order of the O₂ molecule, we can follow these steps:

### Step 1: Understand Bond Order
Bond order is defined as the number of chemical bonds between a pair of atoms. It can be calculated using the formula:
\[ \text{Bond Order} = \frac{1}{2} \times (\text{Number of bonding electrons} - \text{Number of anti-bonding electrons}) \]

### Step 2: Determine the Electron Configuration of Oxygen
The atomic number of oxygen (O) is 8, which means each oxygen atom has 8 electrons. The electron configuration for an oxygen atom is:
\[ 1s^2 \, 2s^2 \, 2p^4 \]

### Step 3: Write the Molecular Orbital Diagram for O₂
In the O₂ molecule, we have two oxygen atoms, so the total number of electrons is:
\[ 8 \, \text{(from one O)} + 8 \, \text{(from another O)} = 16 \, \text{electrons} \]

The molecular orbital filling for O₂ is as follows:
- 1s: 2 electrons (bonding)
- 1s*: 0 electrons (anti-bonding)
- 2s: 2 electrons (bonding)
- 2s*: 0 electrons (anti-bonding)
- 2p: 4 electrons (bonding)
- 2p*: 2 electrons (anti-bonding)

### Step 4: Count the Electrons in Bonding and Anti-bonding Orbitals
- **Bonding Electrons**:
- 1s: 2
- 2s: 2
- 2p: 4
- **Total Bonding Electrons = 2 + 2 + 4 = 8**

- **Anti-bonding Electrons**:
- 1s*: 0
- 2s*: 0
- 2p*: 2
- **Total Anti-bonding Electrons = 0 + 0 + 2 = 2**

### Step 5: Calculate the Bond Order
Using the bond order formula:
\[ \text{Bond Order} = \frac{1}{2} \times (\text{Number of bonding electrons} - \text{Number of anti-bonding electrons}) \]
\[ \text{Bond Order} = \frac{1}{2} \times (8 - 2) = \frac{1}{2} \times 6 = 3 \]

### Conclusion
The bond order of the O₂ molecule is 2. This indicates that there are two bonds between the two oxygen atoms.