What’s a radioactive particle? How does does that article account for the difference between plutonium, uranium, cesium, iodine and their substantial difference

What’s a radioactive particle? How does does that article account for the difference between plutonium, uranium, cesium, iodine and their substantial differences when it comes to their effect on the (human/animal) population. I’ll call any comparison on pure particle count bullshit. There’s no question that coal is a stupid way of generating electricity, but that doesn’t make the dangers of nuclear go away.