Magazine article Science News

Number 117 Joins Element Family: New Superheavy Atom Fills Gap in Chemistry's Periodic Table

Magazine article Science News

Number 117 Joins Element Family: New Superheavy Atom Fills Gap in Chemistry's Periodic Table

Article excerpt

Physicists have reported synthesizing element 117, the latest achievement in their quest to create "superheavy" elements in the laboratory. A paper describing the discovery has been accepted for publication in Physical Review Letters.

A team led by Yuri Oganessian of the Joint Institute for Nuclear Research in Dubna, Russia, created the new element by smashing calcium-48--an isotope with 20 protons and 28 neutrons--and berkelium-249, with 97 protons and 152 neutrons. The collisions created two isotopes of an element with 117 protons.

Sigurd Hofmann, a nuclear physicist at the GSI research center in Darmstadt, Germany, says the work is "convincing."

With rare exceptions, elements heavier than uranium, atomic number 92, must be made in the laboratory.

The Russians collaborated with U.S. researchers, including some from Oak Ridge National Laboratory in Tennessee, where the berkelium was made. Berkelium, atomic number 97, is one of the rare artificially produced elements; the Russian team was able to obtain just 22 milligrams of it from Oak Ridge.

The new element slips into a vacancy in the periodic table between previously discovered elements 116 and 118.

Researchers spotted signs of 117 during two runs of collisions lasting 70 days each. In their paper, the scientists report evidence for a heavier isotope (atomic mass 294) with an inferred radioactive decay half-life of 78 milliseconds. They calculated the half-life of the lighter isotope (atomic mass 293) at 14 milliseconds. …

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