The addition of energy to an atom by x-ray exposure that results in promoting an electron to a higher energy level without removing it is called what?

• A. Excitation
• B. Ionization
• C. Absorption
• D. Scattering

Answer: (A)

Excitation is the process of moving an electron to a higher bound energy level without removing it from the atom. This happens when the energy delivered by the incoming photon matches the energy gap between two bound states, so the electron stays bound to the nucleus but occupies a higher orbital. The atom can later relax back to a lower state, emitting energy in the process. If the energy were sufficient to overcome the binding energy and eject the electron entirely, ionization would occur. Absorption is the general uptake of energy by the atom, but the defining feature here is that the electron remains bound in a higher level, which is exactly what excitation describes. Scattering describes deflection of the photon, not promotion of an electron within the atom.