A team of Russian and American scientists are reporting today that they have created two new chemical elements, called superheavies because of their enormous atomic mass. The discoveries fill a gap at the furthest edge of the periodic table and hint strongly at a weird landscape of undiscovered elements beyond.
The team, made up of scientists from Lawrence Livermore National Laboratory in California and the Joint Institute for Nuclear Research in Dubna, Russia, is disclosing its findings in a paper being published today in Physical Review C, a leading chemistry journal. The paper was reviewed by scientific peers outside the research group before publication.
"Two new elements have been produced," said Walt Loveland, a nuclear chemist at Oregon State University who is familiar with the research. "It's just incredibly exciting. It seems to open up the possibility of synthesizing more elements beyond this."
The periodic table is the oddly shaped checkerboard _ with an H for hydrogen, the lightest element, in the upper-left-hand corner _ that hangs in chemistry classrooms the world over. Each element has a different number of protons, particles with a positive electrical charge, in the dense central kernel called the nucleus.
The number of protons, beginning with one for hydrogen, fixes an element's place in the periodic table and does much to determine an element's chemical properties: ductile and metallic at room temperature for gold (No. 79), gaseous and largely inert for neon (10), liquid and toxic for mercury (80).
Elements as heavy as uranium, No. 92 on the list, are found in nature, and others have been created artificially. But much heavier elements have been difficult to make, partly because they became increasingly unstable and short-lived.
Still, for roughly half a century, nuclear scientists have been searching for an elusive "island of stability," somewhere among the superheavies, in which long-lived elements with new chemical properties might exist.
"We're sort of in the shoals of the island of stability," said Kenton J. Moody, a Livermore nuclear physicist who was one of the experimenters in the work.
"It's an amazing effect," he added. "We're really just chipping away at the edges of it."
The experiments took place at a cyclotron, a circular particle accelerator, in Dubna, where the scientists fired a rare isotope of calcium at americium, an element used in applications as varied as nuclear weapons research and household smoke detectors. Four times during a month of 24-hour-a-day bombardment in July and August, scientists on the experiment said, a calcium nucleus fused with an americium nucleus and created a new element.
Scientists generally do not give permanent names to elements and write them into textbooks until the discoveries have been confirmed by another laboratory. By an international convention based on the numbers, element 113 will be given the temporary name Ununtrium (abbreviated Uut for the periodic table) and element 115 will be designated Ununpentium (Uup).
Loveland said he agreed that the new elements would require independent confirmation before they could receive final acceptance. And he conceded that the Dubna find was likely to receive more than the usual amount of scrutiny: Two years ago, the reported discovery of Element 118 was retracted after a scientist at Lawrence Berkeley National Laboratory was found to have fabricated evidence.
Two new elements, briefly
A Russian particle accelerator appears to have created, for up to 1.2 seconds, previously unseen elements.
1. The nuclei of a calcium atom (left) and an americium atom are smashed into one another.
2. The nuclei and their 115 protons stick together, becoming the first of the new elements.
3. Decay starts in milliseconds: A helium nucleus is ejected, leaving element 113, also new.
4. Helium nuclei continue to fly off until there are 105 protons, making dubnium.
Dubnium decays into two smaller-sized fragments in about a day.
Source: Lawrence Livermore National Laboratory