We are taught that the three basic types of radioactive particles are alpha, beta, and gamma. I know there are other particles, but for now I'm just focusing on these. Alpha particles don't penetrate skin, beta particles do and can cause burns, and gamma rays are very powerful. But my chem book also says that the source of the radiation also determines how dangerous it is. But I don't understand why. Isn't an alpha particle and alpha particle no matter where it came from? Also, why is it safe to handle radioactive isotopes that are shooting our gamma rays? Flinn Scientific sells radioactive sources of Po-210, Sr-90, and Co-60 http://www.flinnsci.com/store/Scripts/prodView.asp?idProduct=17227 [Broken] How is it that they are "safe" even though it's a gamma ray?