atomic orbitals vs. molecular orbitals? [ENDORSED]

[Alison Le 2E]

Hi! Can someone please explain what the difference between electronic transitions in atomic orbitals (atomic spectroscopy) and electronic
transitions in molecular orbitals (molecular spectroscopy) is? (I got this from the quantum world outline and didn't know how to answer it :(..) Thank you!

[Chem_Mod]

Electronic transitions in atomic orbitals (atomic spectroscopy):

Light interacts with electrons in atoms, when the energy per photon matches an energy difference between energy levels in that atom the electron goes to the higher energy level.

Electronic transitions in molecular orbitals (molecular spectroscopy):

Light interacts with electrons in molecules, when the energy per photon matches an energy difference between energy levels in that molecule the electron goes to the higher energy level.

Bonding model: Atoms have atomic orbitals that interact/combine to form bonds (molecular orbitals) in molecules. I'll discuss when we do bonding in class.