Two factors that influence the formation of bonding and antibonding molecular orbitals from atomic orbitals are:
Overlap of atomic orbitals: The extent of overlap between atomic orbitals of the participating atoms determines the formation of bonding and antibonding molecular orbitals. When atomic orbitals overlap constructively, they form a bonding molecular orbital with lower energy and increased electron density between the nuclei. Conversely, when atomic orbitals overlap destructively, they form an antibonding molecular orbital with higher energy and a node or region of electron density that is depleted between the nuclei.
Energy difference between atomic orbitals: The energy difference between the participating atomic orbitals also influences the formation of bonding and antibonding molecular orbitals. If the energy levels of the atomic orbitals are similar, the resulting molecular orbitals will have similar energies, leading to a stronger bonding interaction. However, if the energy levels of the atomic orbitals are significantly different, the resulting molecular orbitals will have different energies, leading to a weaker bonding interaction or even a non-bonding interaction.
Overall, the combination of these two factors determines whether bonding and antibonding molecular orbitals form from atomic orbitals and the nature of the resulting molecular bonding in a chemical system.