Carbon monoxide (CO) is a diatomic molecule with the following properties:
1. Molecular Configuration:
The molecular orbital configuration of CO can be derived from the combination of atomic orbitals of carbon and oxygen. The electron configuration for carbon (C) is \(1s^2 2s^2 2p^2\) and for oxygen (O) it is \(1s^2 2s^2 2p^4\).
In the CO molecule, the molecular orbital filling follows this sequence:
- The bonding order and orbital energies are similar to homonuclear diatomic molecules.
- The molecular orbitals in order of increasing energy are:
- \( \sigma_{1s} \)
- \( \sigma_{1s}^* \)
- \( \sigma_{2s} \)
- \( \sigma_{2s}^* \)
- \( \sigma_{2p_z} \)
- \( \pi_{2p_x} \)
- \( \pi_{2p_y} \)
- \( \pi_{2p_x}^* \)
- \( \pi_{2p_y}^* \)
The molecular orbital filling for CO:
- From Carbon: 2 electrons from \(1s\), 2 from \(2s\), and 2 from \(2p\)
- From Oxygen: 2 electrons from \(1s\), 2 from \(2s\), and 4 from \(2p\)
The total number of available electrons in CO is \(10\) (6 + 4). The filled orbitals are:
- \(1s^2\)
- \(1s^{*2}\)
- \(2s^2\)
- \(2s^{*2}\)
- \(2p_z^2\) (bonding)
- \(2p_x^2\) (bonding)
- \(2p_y^0\) (empty)
2. Number of Bonding Electrons:
The bonding electrons are in the bonding molecular orbitals:
- \( \sigma_{2s} \): 2 electrons
- \( \sigma_{2p_z} \): 2 electrons
- \( \pi_{2p_x} \): 2 electrons
- \( \pi_{2p_y} \): 0 electrons (this is empty)
Total bonding electrons = \(2 + 2 + 2 = 6\)
3. Number of Anti-bonding Electrons:
The anti-bonding electrons are found in the anti-bonding molecular orbitals:
- \( \sigma_{1s}^* \): 2 electrons (but this is below the reference level and does not facilitate bond formation)
- \( \sigma_{2s}^* \): 2 electrons
- \( \pi_{2p_x}^* \): 0 electrons
- \( \pi_{2p_y}^* \): 0 electrons
Total anti-bonding electrons = \(2 + 2 + 0 + 0 = 4\)
4. Bond Order:
The bond order can be calculated using the formula: \[ \text{Bond Order} = \frac{(N_b - N_a)}{2} \] Where \(N_b\) is the number of bonding electrons and \(N_a\) is the number of anti-bonding electrons.
Here, \(N_b = 6\) and \(N_a = 4\), \[ \text{Bond Order} = \frac{(6 - 4)}{2} = \frac{2}{2} = 1 \]
Summary:
- Molecular Configuration: \( (1s^2) (1s^{*2}) (2s^2) (2s^{*2}) (2p_z^2) (2p_x^2) (2p_y^0) \)
- Number of Bonding Electrons: 6
- Number of Anti-bonding Electrons: 4
- Bond Order: 1
Thus, Carbon monoxide (CO) exhibits a bond order of 3, signifying a triple bond between carbon and oxygen.