Video Transcript
The diagram shows two hydrogen atoms. In both atoms, the energy of their electron changes.
Let’s look at the different parts of this question one by one, starting with the first.
Is the change in the electron energy in atom I consistent with the absorption of a photon?
In atom I, we see that there was an electron in the first energy level that then moves to the second energy level. This change in energy by transitioning to a higher energy level is something that typically occurs when an electron absorbs a photon, causing it to enter in excited state, which is exactly what we see here in atom I. This means that, yes, the change in the electron energy in atom I is consistent with the absorption of a photon.
Now, the second part of this question asks, is the change in the electron energy in atom II consistent with the absorption of a photon?
In atom II, we see that the electron starts in the second energy level and then transitions downwards to the first energy level. In these cases where an electron transitions from a higher to a lower energy level, absorption is not involved, even if a photon might be. For example, in stimulated emission, a photon can interact with an already-excited electron and cause it to transition down to a lower energy level, causing the electron to release a photon with the same energy, direction, and phase as the photon that stimulated it. But this was not caused by an absorption. This was caused by a stimulation. So the change in the electron energy in atom II is not consistent with the absorption of a photon.
Looking now at the third part of the question, is the change in the electron energy in atom I consistent with the emission of a photon?
Both types of emission, which are stimulated and spontaneous, require a transition to a lower energy level from an excited state in order to release a photon. So transitioning upwards to a higher energy level into an excited state cannot cause the emission of a photon since both types of emission require the opposite to occur. So, no, the change in the electron energy in atom I is not consistent with the emission of a photon.
However, for the last part of this question “Is the change in the electron energy in atom II consistent with the emission of a photon?” we can already see that it ought to be, since both types of photon emission require an electron to transition to a lower energy level, which is what is happening in atom II. So, yes, the change in the electron energy in atom II is consistent with the emission of a photon.
