



Scientists have been creating new elements since 1940, when neptunium and plutonium were first forged at the University of California, Berkeley. As more elements have been created, a pattern emerged: Each new element was radioactive, slightly heavier than the one before, and in general, more unstable.

Eventually, scientists hope to discover new elements that might be stable, easily studied and, perhaps, offer commercially useful properties.

Two man-made elements, Nos. 114 and 116, were added to the periodic table after a collaboration between Russian and U.S. scientists that began in 1990 at this cyclotron in Dubna, Russia. Lawrence Livermore National Laboratory

Atoms of the two new elements—created in a clash of nuclear particles—lasted only milliseconds before decaying into simpler and more stable substances, making them hard to study and even harder to verify.

The panel responsible for certifying claims of new elements took three years to confirm the discoveries. Claims involving three other new elements—113, 115 and 118—were rejected.

"We have to take things one atom at a time," said Paul Karol, a nuclear chemist at Carnegie Mellon University who is chairman of the international panel.

Elements are pure chemical materials from which all known matter is composed. They consist of a single type of atom distinguished by the number of protons in its nucleus, its atomic number. The periodic table arranges the elements based on their atomic number and allows scientists to predict as-yet-undiscovered elements.

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