In a nutshell:
- Molecular orbitals are formed by 2 overlapping atomic orbitals.
- There are 4 orbitals (s,p,d and f) and all orbitals can only contain 2 electrons
- In orbitals, electrons must be filled from the lowest energy level and lose from the highest energy level.
- In all orbitals with the same energy level, all of them must be filled with half-spin before they can be paired up with another electron.
- There are 3 molecular orbitals (bonding orbital, anti-bonding orbital and non-bonding orbital).
- When 2 atomic orbitals overlap they react in 2 different forms, the in-phase or out-of-phase form with in turns lead to the bonding orbital or anti-bonding orbital
- In-phase interaction leads to an increase in the intensity of the negative charge in the region where they overlap.
- This creates an increase in negative charge between the nuclei and an increase in the attraction between the electron and the nuclei for the atoms and energy would be required to shift the electrons back into the 1s orbitals of separate atoms.
- This keeps the atoms together in the molecule, so we call this orbital a bonding molecular orbital.
- The out-of-phase interaction leads to a decrease in the intensity of the negative charge.
- This creates a decrease in negative charge between the nuclei and a decrease in the attraction between the electron charge and the nuclei for the atoms in the bond and electrons are more stable in the 1s atomic orbitals of separate atoms
- This keeps the atoms together in the molecule, so we call this orbital an anti-bonding molecular orbital.
- If the bonding interactions outnumber the anti-bonding interactions, the molecular orbital is said to be "bonding," while if the anti-bonding interactions outnumber the bonding interactions, the molecular orbital is said to be "anti-bonding"
