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.
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.