Energy level after photon absorbtion

[Johnahh]

Main Question or Discussion Point

Say a photon was absorbed by an electron at 1s in an oxygen atom but it only had enough energy to move it to another energy level that was already occupied such a 2s etc. What happens to this photon?

 

[mfb]

The photon does not get absorbed if there is no available unoccupied energy level for the electron.

 

[Johnahh]

so how does the electron know that the photon does not have enough energy to move it to a free orbital?

 

[mfb]

Quantum mechanics. If a process is impossible, it just does not happen.