A List of Radioactive Man-Made Elements


An atom's atomic number -- the number of protons in its nucleus -- determines what element it is. Researchers produce synthetic elements by bombarding an existing element with protons, neutrons or the nuclei of smaller atoms. The nucleus of the existing element incorporates these particles in a process called fusion, thereby changing the atomic number and creating a new element. All elements heavier than uranium (chemical symbol "U") are man-made; plutonium also occurs naturally but only in tiny amounts. Most synthetic elements are extremely short-lived and break down into smaller atoms after a few milliseconds. But some, like plutonium, americium and technetium, have found commercial, scientific and medical uses.


  • Taking its name from the Greek word "technetos," meaning artificial, technetium (Tc) was the first synthetically produced element. In 1937, researchers Carlo Perrier and Emilio Segre discovered technetium after bombarding a sample of molybdenum with deuterium nuclei. Doctors and medical researchers use minute amounts of this silvery-grey metal as a radioactive tracer to detect certain illnesses and to monitor body functions. Engineers use technetium to calibrate machinery, and small concentrations of technetium oxide can protect steel and iron from corrosion.


  • Uranium, with an atomic number of 92, is the heaviest known naturally occurring element. Neptunium (Np) was the first synthesized transuranium (after uranium) element. Working at the University of California's Berkeley Radiation Laboratory, Edwin McMillan and Philip H. Abelson produced Neptunium by bombarding uranium with neutrons. They named the new element Neptunium after the planet Neptune, the next planet after uranium's namesake Uranus.


  • First produced in 1940 by a research team including Glenn Seaborg, Edwin McMillan, Joseph Kennedy and Arthur Wahl, plutonium (Pu) takes its name from the planet Pluto, following in line with uranium and neptunium. Researchers discovered that bombarding the heavy, unstable element with slow neutrons caused it to break down in a fission chain reaction, releasing incredible amounts of energy. Nuclear power plants us a controlled plutonium fission reaction to produce electricity, and an uncontrolled fission chain reaction releases the destructive force of the atomic bomb.


  • Working in 1944 at the University of Chicago, the researchers Seaborg, James and Morgan initially referred to americium (Am) as "pandemonium" due to the difficulties they experienced trying to isolate the new element. Ionization chamber smoke detectors contain small amounts of this silvery-white, highly radioactive metal in the form of americium dioxide. One gram of americium dioxide can produce over three million household smoke detectors.

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