Plutonium: The Firstborn of Alchemy 

Regardless of its scary reputation, plutonium is one of the most unique and interesting elements. Plutonium is a man-made element and a live proof that transmutation of one element into another is possible - the belief that made alchemy so unpopular among true scientists. I guess the prospect of turning lead into gold looks far more exciting than turning uranium into highly poisonous plutonium, but it is because of high efficiency and radioactivity of plutonium current Curiosity expedition became possible. Long time ago when the metal was just discovered, and produced for the first time in 1940, the entire supply of Great Britain consisted of ten milligrams of plutonium; today hundreds of tons are being produced and stored by US along. Plutonium is dangerous, very dangerous; it is radioactive and poisonous at the same time. As a metal, plutonium is incredibly dense and hard, the golf ball size piece of it would weigh over couple pounds and you can easily ruin your hack saw blade trying to cut it.