Hello everybody :) I've been wondering about how radiation is harmful for living beings... I know that the three kinds of radiation (α, β, γ). α radiation composed of helium nuclei (2 protons and 2 neutrons), β radiation is composed by the emission of electrons, caused by the conversion of neutrons into protons in an atom's nuclei, and gamma radiation emission occurs by itself (in form of packages called photons as long as I know) during radioactive decay, but also happen more frequently during emission of α and β particles. I've got a few questions.. 1. Let's put for example 212Rn, witch has an half life of 24 minutes, meaning that half of the 212Rn will loose 2 protons and 2 neutrons every 24 minutes, and will so form 208Po. It's obvious that 212Rn is highly radioactive, But why is 235U, for example, more harmful, even having a decay from billions of years? 2. Witch radiation is more dangerous for living beings? α particles are MASSIVE compared to β, about 7220 times heavier, but have although very small penetration power and short range, due to its size, witch makes α particles ionize a large number of atoms during its travel, but ending at Ek=0 (excluding controlled acceleration of α particles) ; β particles are much smaller then α particles and do so travel longer distances, being able to cause ionization in long range but not necessarily in large scale; gamma radiation is an electromagnetic wave witch must transport more eV then necessary for causing an orbiting electron to release itself from the nuclei, ionizing the atom. This told, I can't really get a picture of witch kind of radiation can cause more damage under same circumstances and under natural velocity standards? 3. now a strange question :P Why do uranium bars, witch are cooled in water chambers in nuclear reactors, burn the skin and also cause it to peel off like a piece of paper when we pick it up from a table? :) Thanks for taking the time of reading! Have a nice day!