To calculate the molecular orbital energy diagram and electronic structure of the H2O molecule using the LCAO method, we first need to consider the atomic orbitals of the constituent atoms, hydrogen H and oxygen O .
1. Atomic orbitals:
– Hydrogen has one 1s orbital.
– Oxygen has the following orbitals: 1s, 2s, and three 2p orbitals 2px, 2py, 2pz .
2. Formation of molecular orbitals:
– Two hydrogen 1s orbitals combine with the oxygen 2s and one of the 2p orbitals let’s say 2pz to form three molecular orbitals: one bonding σ , one non-bonding n , and one antibonding σ* .
– The remaining two oxygen 2p orbitals 2px and 2py remain non-bonding orbitals.
3. Filling electrons in molecular orbitals:
– H2O has a total of 10 electrons 2 from each hydrogen and 6 from oxygen .
– According to the aufbau principle, electrons fill the molecular orbitals in increasing order of energy.
– The filling order is: σ 2 electrons , n 2 electrons , 2px 2 electrons , 2py 2 electrons , and σ* 2 electrons .
4. Molecular orbital energy diagram:
– The energy levels of the molecular orbitals can be represented as follows from lowest to highest energy : σ < n ≈ 2px ≈ 2py < σ*.
– The diagram shows the bonding σ , non-bonding n, 2px, 2py , and antibonding σ* molecular orbitals, with the number of electrons in each orbital indicated.
5. Electronic structure:
– The electronic structure of the H2O molecule can be represented as: σ ² n ² 2px ² 2py ² σ* ².
In summary, the molecular orbital energy diagram and electronic structure of the H2O molecule using the LCAO method show one bonding, three non-bonding, and one antibonding molecular orbitals, with a total of 10 electrons distributed among them.
