#alpha-"particles"# are essentially helium ions, and these are MASSIVE, and are POORLY penetrating.
#beta-"radiation"# are fast moving electrons, and these are slightly more penetrating with respect to #alpha"-particles"#.
And #gamma-"radiation"# are faster moving particles, on the photonic scale. And these are the most penetrating particles. They require lead shielding of several mm for safe containment. If you think of Dr Bruce Banner, who was poisoned by gamma rays to become the #"Incredible Hulk"#, the strongest and coolest superhero, this might stick in your memory. And of course the order of penetration also follows the Greek alphabet.