Question

In a hypothetical (?) Og2+235 we would have a simple sigma bonding orbital occupied by one electron (leading to a bond order of 1/2). But how to take into account the giant repulsion of the two nuclei? Generally how are nucleis taken into account for energy calculations from molecular orbitals in MO theory? So far I've always read about the electrons but very few about the nuclei in the system.

Same in He23+, half bond order but very large repulsion. My intuition says that He21+ should be more stable, even if both have the same bond order.

Where in the framework of MO theory is exactly that taken into account? How does nuclei repulsion change the MO energy scheme?

Answer 1

MO Theory includes nuclear repulsion in the potential energy, which is reflected in the energy-level diagrams used to predict molecular stability. Bond order is important but doesn't fully determine stability due to nuclear and electron interactions that must be considered.

Step-by-step explanation:

In the framework of Molecular Orbital (MO) Theory, nuclei repulsion is taken into account when calculating the energy of the system. This is represented in the potential energy which is higher due to the repulsion between the positively charged nuclei.

For instance, even though He22+ and He2+ have a bond order of 1/2, the giant nuclear repulsion in He22+ makes it less stable than He2+. The molecular orbitals are designed to incorporate nuclear attractions, which stabilize the bonding orbitals, and nuclear repulsions, which destabilize antibonding orbitals, resulting in different energy levels for these orbitals.