Which statement best describes alpha particles?

Which statement best describes alpha particles?

• A. Low ionizing and highly penetrating.
• B. Highly ionizing and highly penetrating.
• C. Highly ionizing and weak penetrating.
• D. Low ionizing and weak penetrating.

Answer: (C)

Alpha particles are helium nuclei, carrying a +2 charge and relatively large mass. This combination makes them interact very strongly with matter, producing many ion pairs in a very short path. That dense ionization is what we mean by highly ionizing. At the same time, their heaviness causes them to lose energy quickly and travel only a short distance in material, so they don’t penetrate far—outside a few centimeters in air or a thin barrier like paper, they’re halted. So they’re capable of a lot of ionization, but their penetrating power is weak. (For comparison, lighter beta particles are more penetrating but less ionizing, while gamma rays are penetrating but ionize less per unit length.)

Alpha particles are helium nuclei, carrying a +2 charge and relatively large mass. This combination makes them interact very strongly with matter, producing many ion pairs in a very short path. That dense ionization is what we mean by highly ionizing. At the same time, their heaviness causes them to lose energy quickly and travel only a short distance in material, so they don’t penetrate far—outside a few centimeters in air or a thin barrier like paper, they’re halted. So they’re capable of a lot of ionization, but their penetrating power is weak. (For comparison, lighter beta particles are more penetrating but less ionizing, while gamma rays are penetrating but ionize less per unit length.)