What is the highest occupied molecular orbital in the o2 molecule?

HOMO

Oxygen molecule i.e. O₂ has total 16 electrons.

Electron configuration of O₂ is 1s² 2s² 2p⁴

On placing the electrons in molecular orbitals according to Aufbau's Principle and Hund's Principle. So, there are two electrons in the orbital that is the highest occupied molecular orbital.

Hence O₂ is paramagnetic in nature since it has two unpaired electrons.

Learn more:

link

H2 is known to exist. For dihydrogen, H2, we can identify the frontier molecular orbitals (FMOs). The highest occupied molecular orbital (or HOMO) is the σ (sigma) 1s MO. The lowest unoccupied MO (LUMO) is the σ* (sigma star) 1s MO which is antibonding.

i don t now