Penetrating ability:
Radioactivity's capacity to penetrate through materials is referred to as its penetrating ability. The capacity to penetrate is proportional to the magnitude of the radioactive particle.

Alpha particle:
1. The largest particles constitute alpha particles, beta particles are significantly smaller, and gamma rays have no mass.

2. The larger the particle, the further probable it is to collide well with a substance's atoms. The impact will cause the particle to cease moving through the substance.

Therefore, alpha radiations have the least penetrating power as they are massive in nature.