Scientists create new element 113: how large an atom nucleus could be

Element 113 is an atom with 113 protons in its nucleus -- a type of matter that must be created inside a laboratory because it is not found naturally on Earth. Heavier and heavier synthetic elements have been created over the years, with the most massive one being element 118, temporarily named ununoctium.

But element 113 has been stubbornly hard to create. After years of trying, researchers at the RIKEN Nishina Center for 

Accelerator-Based Science in Japan said today (Sept. 26) they finally did so. On Aug. 12, the unstable element was formed and quickly decayed, leaving the team with data to cite as proof of the accomplishment.

Elements starting with hydrogen, with the atomic number of 1, through to plutonium, 94, exist naturally. Those from 95 through the 116 have been created and confirmed, excluding those with the atomic numbers of 113 and 115.

How 113 Was Made

Kosuke Morita and his team collided zinc nuclei (30 protons) with a thin layer of bismuth (83 protons) to form nuclei with 113 protons. The nuclei underwent alpha decay, turning element 113 into element 111, 109, 107, 105, 103 and element 101, Mendelevium.

The RIKEN Linear Accelerator Facility outside of Tokyo, in which element 113 has been discovered and confirmed (Photo: RIKEN)

"For over nine years, we have been searching for data conclusively identifying element 113, and now that at last we have it, it feels like a great weight has been lifted from our shoulders," Kosuke Morita, leader of the research group, said in a statement. 

If confirmed, the achievement will mark the first time Japan has discovered a new element, and should make Japan the first Asian country with naming rights to a member of the periodic table. Until now, only scientists in the United States, Russia and Germany have had that chance.

"I would like to thank all the researchers and staff involved in this momentous result, who persevered with the belief that one day 113 would be ours," Morita said. "For our next challenge, we look to the uncharted territory of element 119 and beyond."

Dr. Kosuke Morita of the RIKEN Nishina Center for Accelerator-based Science (Photo: RIKEN)

Scientists are continually trying to create bigger and bigger atoms, both for the joy of discovery and for the knowledge these new elements can offer about how atoms work.

Most things in the universe are made of very simple elements, such as hydrogen (which has one proton), carbon (six) and oxygen (eight). For each proton, atoms generally have roughly the same number of neutrons and electrons. Yet the more protons and neutrons that are packed into an atom's nucleus, the more unstable the atom can become. Scientists wonder if there is a limit to how large atoms can be.

The decay chain for ununtrium-278, as confirmed by the known alpha decay of Db-262 into Lw-258, and that of Lw-258 into Md-254 (Image: RIKEN)

Synthesis and beginning of the decay chain for element 113 (Image: RIKEN)

The first synthetic element was created in 1940, and so far 20 different elements have been made. All of these are unstable and last only seconds, at most, before breaking apart into smaller elements.

To synthesize element 113, Morita and his team collided zinc nuclei (with 30 protons each) into a thin layer of bismuth (which contains 83 protons). When 113 was created, it quickly decayed by shedding alpha particles, which consist of two protons and two neutrons each. This process happened six times, turning element 113 into element 111, then 109, 107, 105, 103 and finally, element 101, Mendelevium (also a synthetic element).

Morita's group seemed to create element 113 in experiments conducted in 2004 and 2005, but the complete decay chain was not observed, so the discovery couldn't be confirmed. Now that this specific pattern resulting in Mendelevium has been seen, the scientists say it "provides unambiguous proof that element 113 is the origin of the chain."

Limit to how large atom can be:

Scientists have long wondered whether there is a limit to the number of protons and neutrons that can be clustered together to form the nucleus of an atom. A new study comes closer than ever to finding the answer by estimating the total number of nucleus variations that can exist.

The periodic table of elements includes 118 known species of atoms, and each of these exists (either naturally or synthetically) in several versions with differing numbers of neutrons, giving rise to a total of about 3,000 different atomic nuclei. As technology has improved over the years, physicists have been building heavier and heavier atoms — element 117 was created only last year, and researchers are hot on the trail of 119. New projects are in the works to add and subtract neutrons to known elements to create ever more exotic variations, known as isotopes. 

 In an issue of the journal Nature, researchers report that roughly 6,900 nuclides (variations of atomic nuclei), plus or minus 500, should be possible.

"Beyond the 7,000, we are talking about nuclides whose lifetimes can be so short that they can't form," said research team member Witold Nazarewicz of the University of Tennessee, the Oak Ridge National Laboratory in Tennessee and Warsaw University in Poland. "The system would decay instantly."

Even within those 7,000, the vast majority would be unstable, lasting only a tiny fraction of a second.  Of the 3,000 known nuclides, only 288 are stable.

Atoms are limited in the number of protons they can contain, because each proton is positively charged, and because "like repels like," they want to push each other away. Even neutrons, which have no charge, are slightly repulsive to each other. A mysterious force called the strong interaction, which is about 100 times stronger than electromagnetism, is what binds protons and neutrons together in nuclei.

"The nature or the exact form of the strong force, especially in heavier nuclei, is still a subject of very intense experimental and theoretical research," Nazarewicz told LiveScience.