http://news.bbc.co.uk/2/hi/science/nature/8093374.stm
Periodic table gets a new element
The ubiquitous periodic table will soon have a new addition - the “super-heavy” element 112.
More than a decade after experiments first produced a single atom of the element, a team of German scientists has been credited with its discovery.
The team, led by Sigurd Hofmann at the Centre for Heavy Ion Research, must propose a name for their find, before it can be formally added to the table.
Scientists continue the race to discover more super-heavy elements.
Professor Hofmann began his quest to add to the periodic table in 1976.
The fusion experiments he and his colleagues carried out at the centre have already revealed the existence of elements with atomic numbers 107-111.
These are known as “super-heavy elements” - their numbers represent the number of protons which, together with neutrons, give the atom the vast majority of its mass.
To create element 112, Professor Hofmann’s team used a 120m-long particle accelerator to fire a beam of charged zinc atoms (or zinc ions) at lead atoms. Nuclei of the two elements merged, or fused, to form the nucleus of the new element.
These very large and heavy nuclei are also very unstable. They begin to fall apart or “decay” very soon after being formed - within a few milliseconds, in this case.
This releases energy, which scientists can measure to find out the size of the decaying nucleus.
But such experiments produce very few successful fusions, and scientists need increasingly powerful accelerators to run experiments for longer and find the elusive, unstable elements.
This is why it took such a long time for element 112 to be officially recognised by the International Union of Pure and Applied Chemistry (IUPAC).
Its discovery had to be independently verified, and so far only four atoms have ever been observed.
IUPAC temporarily named the element ununbium, as “ununbi” means “one one two” in Latin; but Professor Hofmann’s team now has the task of proposing its official name.
He is currently keeping the shortlist under wraps.
Working together
Teams in Russia, the US and Japan are taking part in what Professor Hofmann described as the “friendly competition” to discover new, heavier elements.
In 2006, Professor Hofmann’s competitors at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, claimed the discovery of element 118. It was made by bombarding a californium target with a beam of calcium ions.
“We have confirmed some of these results,” Professor Hofmann told BBC News.
But he is now setting his sights higher. “We tried the same experiment to get to element 120. We’ve not seen it yet, but we believe the element exists and, with a long enough beam time, it could be produced,” he said.
“It’s certainly a race, and it’s nice to be first.”
