What is radiation?

[matt_london]

<PRE>What properties does a radioactive material have over say iron?</PRE>

[Clanad]

Looseheads description of half-life in the question just above, contains the answer to your question as well. Iron for example (Fe chemically) contains a determined number of protons and neutrons... the exact number of these subatomic particles contained in the neucleus determines the identity of the iron, e.g., iron-56 for iron samples containing 26 protons and 36 neutrons. These can, if unstable, decay by ejecting some of the subatomic particles. This causes the iron to become something else over a period of time called (ala Loosehead) half-life. Well, guess what, the half life of iron is fairly low... around 1.5 million years, whereas the half-life of uranium-238 (used for weapons) is 4.5 billion years. So... long way of saying iron has lost most of its radioactivity and plutonium has not...