What is the bond order between C and O in `CO` ?

Answer

To find the bond order between carbon (C) and oxygen (O) in the carbon monoxide (CO) 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:
\[ \text{Bond Order} = \frac{(\text{Number of bonding electrons} - \text{Number of antibonding electrons})}{2} \]

### Step 2: Determine the Electron Configuration
The electron configuration of carbon (C) is \(1s^2 2s^2 2p^2\) and for oxygen (O) it is \(1s^2 2s^2 2p^4\).

### Step 3: Construct the Molecular Orbital Diagram
In CO, the molecular orbitals are filled as follows:
- The bonding molecular orbitals (σ and π) are filled first.
- The anti-bonding molecular orbitals (σ* and π*) are filled last.

### Step 4: Count the Electrons
In the CO molecule:
- Carbon contributes 4 valence electrons (2 from 2s and 2 from 2p).
- Oxygen contributes 6 valence electrons (2 from 2s and 4 from 2p).
- Total valence electrons = 4 (from C) + 6 (from O) = 10 electrons.

### Step 5: Fill the Molecular Orbitals
The molecular orbitals will be filled in the following order:
1. σ(1s) - 2 electrons
2. σ*(1s) - 0 electrons
3. σ(2s) - 2 electrons
4. σ*(2s) - 0 electrons
5. σ(2p) - 2 electrons
6. π(2p) - 4 electrons (2 for each π bond)

### Step 6: Calculate Bonding and Antibonding Electrons
- Bonding electrons = 2 (σ(2p)) + 4 (π(2p)) = 6
- Antibonding electrons = 0

### Step 7: Apply the Bond Order Formula
Using the bond order formula:
\[ \text{Bond Order} = \frac{(6 - 0)}{2} = 3 \]

### Conclusion
The bond order between carbon and oxygen in the CO molecule is 3, indicating that there are three bonds (one triple bond) between the two atoms.

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