Radioactive Isotopes

• Atoms consist of a cloud of electrons surrounding a nucleus containing some number of protons and neutrons. The number of protons and electrons is equal, but the number of neutrons can vary -- those are isotopes. Polonium, for example, has 84 protons, but it also has isotopes with as few as 126 and as many as 134 neutrons. Not all isotopes are unstable, but many are. All of polonium's isotopes, for example, are unstable. An unstable isotope will eventually change -- decay into another atom -- and release radiation.
  
  

Types of Radiation

• In the days of the discovery of radioactivity, the first characteristic scientists noticed was that radioactive materials release high energy, energy that radiates away and was thus labelled "radiation." The second characteristic noted was that radiation comes in three types: alpha radiation has a positive charge, gamma radiation has no electric charge and beta radiation has a negative charge. Since then, alpha particles have been identified as consisting of two protons and two neutrons, gamma radiation as very high-energy photons and beta particles as electrons.
  
  

Radiation Characteristics

• Imagine that a material -- a piece of paper, plastic, metal, whatever -- at the microscopic level looks like a brick wall with some of the bricks replaced by thin panes of glass. Alpha particles are like cannonballs: They hit the wall and do a lot of damage, but they don't make it past the wall. Beta particles are like BBs shot out of a Red Ryder BB gun: They can break through a pane of glass, then maybe break through a few more, not doing a whole lot of damage, but making it through more layers than an alpha particle. A gamma ray is like a hot laser that burns right through 1, 10, maybe even 30 or 40 layers of windows before it finally is too weak to continue.
  
  

Radiation Together

• Usually an isotope will either release an alpha particle or a beta particle. Whichever it releases, almost always a gamma ray is released as well. But if there are several isotopes mixed together (as is very often the case), then alpha, beta and gamma radiation will all be released simultaneously. It's kind of like when a car explodes. Hunks of flying metal, shards of shooting glass and a shock wave will all strike against people standing nearby. If someone is hit only by glass or only shards of metal or both, they're going to be hurt. That's the same thing that happens when alpha and beta particles are emitted together: The presence of one particle doesn't make the other particle any more dangerous, but they're each dangerous enough on their own.
  
  

Staying Safe

• Neither alpha particles nor beta particles pose a very serious risk to the body. Alpha particles will get stopped by something as thin as a few pieces of paper. Beta particles are blocked by just a few millimeters of aluminum. So if beta and alpha particles are together, they can both be shielded fairly easily. Inside the body, it's a completely different story. Ingesting or inhaling alpha or beta decay isotopes can be extremely serious. And the gamma rays that come along with the alphas and betas are dangerous inside or outside the body.