The penetrating power (R) and ionizing power (I) of α, β, and γ rays follow the ordering

Concept:

α particles: during radio active decay they are ejected from the nucleus of an atom and travels very less in the air

β particles: electrons ejected from the nucleus of a radio active atom and travel farther in the air than α particles therefore can penetrate upto half inches into the body through skin

γ particles: ejected from the nucleus of a radio active atom after α, and β particles and travels up to ten yards or more in the air. They can easily penetrate into the body

Explanation:

Penetration power of α, β and γ particles: the ability of any radiation or particle to pass through a matter is called penetrating power. 

α particles: since they travel very less into the air, their penetration power is very low and can be easily shielded by a piece of paper

β particles: they can pass the paper but can be blocked by aluminum foil

γ particles: to stop these a thick dense material of concrete or lead is required

The order of penetration is:

\(R_{α}< R_{β}< R_{γ} \)

Ionization power of α, β and γ particles: the ionization power is the power to emit an electron from an atom and it is directly proportional to the mass of the particle.

As α particles are highest in mass followed by β and γ particles, they have the highest ionizing power therefore the ionization power order is:

\(I_{\gamma}< I_{\beta}< I_{\alpha} \)

Conclusion:

Therefore the penetrating power (R) and ionizing power (I) of α, β, and γ rays follow the order Rγ > Rβ > Rα and lα > lβ > lγ