What happens when an electron in an outer shell absorbs a photon of electromagnetic energy?

What happens when an electron in an outer shell absorbs a photon of electromagnetic energy?

• A. Promoted to a higher energy shell
• B. It is ejected from the atom
• C. The nucleus captures the energy
• D. It changes its spin

Answer: (A)

When atoms have electrons in discrete energy levels, absorbing light can only cause transitions between those levels if the photon's energy matches the difference between two allowed states. If an electron in an outer shell absorbs a photon whose energy equals the gap to a higher bound level, it gains that energy and moves up to a higher energy shell. This is excitation, not ionization, because the electron remains bound to the atom in a higher orbital. That’s why promoting to a higher energy shell is the correct outcome here. If the photon had enough energy to exceed the binding energy, it could eject the electron (ionization) instead, which is a different process. The nucleus doesn’t capture energy in this scenario, and changing the electron’s spin is not the primary consequence of simple photon absorption. After excitation, the electron may later relax back down, emitting a photon in the process.

When atoms have electrons in discrete energy levels, absorbing light can only cause transitions between those levels if the photon's energy matches the difference between two allowed states. If an electron in an outer shell absorbs a photon whose energy equals the gap to a higher bound level, it gains that energy and moves up to a higher energy shell. This is excitation, not ionization, because the electron remains bound to the atom in a higher orbital.

That’s why promoting to a higher energy shell is the correct outcome here. If the photon had enough energy to exceed the binding energy, it could eject the electron (ionization) instead, which is a different process. The nucleus doesn’t capture energy in this scenario, and changing the electron’s spin is not the primary consequence of simple photon absorption. After excitation, the electron may later relax back down, emitting a photon in the process.