The periodic table of the elements is slowly getting bigger. At one time it contained only 83 naturally occurring elements, starting with hydrogen and ending with uranium. These elements have half-lives that are comparable to the age of the Earth, which is about 4.5 billion years old. Since the 1940s, however, physicists have been able to produce unstable elements that decay to lighter elements on timescales that can range from thousands of years to tiny fractions of a second. By last year a total 114 elements were known, and earlier this year the author and co-workers reported the synthesis of two new "superheavy" elements.
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