Final answer:
Electron impact ionization occurs when a high-energy electron collides with an atom and ejects one of its electrons, creating a positively charged ion. The degree of ionization increases with the temperature of the gas. Electrons absorb more energy than nuclei when interacting with ionizing radiation due to their lower mass.
Step-by-step explanation:
Electron impact ionization is a process where an energetic electron collides with an atom, providing sufficient energy to knock an electron out from the atom's orbital shell. This results in the formation of an ion, specifically a positively charged ion since the atom has lost an electron. As an atom absorbs discrete amounts of energy, it may just move an electron to a higher orbital (excitation), or if the energy is high enough, it can completely remove an electron, leading to ionization. The ionization energy is the minimum energy required to achieve this. A subsequent process can occur where the now ionized atom captures another electron, and during this recapture the energy released may emit a high-energy electromagnetic (EM) wave, such as an X-ray.
The temperature of the gas matters considerably because it impacts the speed at which atoms move; faster movement at higher temperatures increases the likelihood of collisions and thus ionization. When considering the interaction with ionizing radiation, electrons tend to absorb more energy as compared to nuclei due to the law of conservation of momentum and energy. The lighter mass of electrons allows them to gain more speed and hence more kinetic energy from these interactions.