On the periodic table of elements there sat a placeholder in position 112, ununbium, an indication that something should go there. What that something should be, though, has been at the centre of 16 years of controversy, which all began with a beam of zinc atoms.
Anyone who survived high school chemistry is probably familiar with the periodic table of elements, that frustratingly complex, yet elegantly organized aggregation of letters and numbers describing all of the known elements. What you might be surprised to learn is that several of the elements, 26 of them in fact, do not occur in practical numbers anywhere but in nuclear reactors, particle accelerators and perhaps stars.
The first of these synthetic elements, technetium, was discovered in 1937, but had been theorized to exist since the mid-19th century due to a gap between molybdenum (atomic number 42) and ruthenium (atomic number 44) on the periodic table. Researchers at the University of Palermo, in Sicily, noticed that a thin piece of molybdenum foil, which had been part of a particle accelerator, had started to give off a strange form of X-ray radiation.
Upon further examination, it was found that by bombarding the foil with deuterons (particles consisting of a neutron and a proton), the researchers had serendipitously added protons and neutrons to the nucleus of the molybdenum, creating technetium.
Despite being synthetic, technetium is an important element for nuclear medicine. In fact, several synthetic elements — such as plutonium and americium — have been found to be useful in applications as diverse as nuclear weapons and smoke detectors. However, the majority of the synthetic elements are not useful for much other than theoretical chemistry, and only last for minute fractions of seconds following their creation. Element 112 is one such atom.
In 1996, 112 was found by Sigurd Hofmann, and his team in Germany at the Centre for Heavy Ion Research (GSI). Sigurd fired zinc atoms at a piece of lead and noticed that an atom was created which decayed into nobelium (atomic number 102) in stages, by releasing alpha particles (helium atoms that have been stripped of their electrons). By counting the number of decay stages in the chain, Hofmann concluded that the starting element had an atomic number of 112, and was a never before seen atom.
However, when Hofmann submitted his findings to the International Union of Pure and Applied Chemistry (IUPAC) problems were found with the proposed decay chain. One of these problems was an inconsistency with one of the stages of decay — the transition from rutherfordium to nobelium didn’t match known patterns. Also, in some instances, the decay stopped before reaching nobelium. Based on these inconsistencies, 112 was denied its spot on the periodic table.
This rejection prompted Hofmann and his team to reanalyze the raw data from their experiments, which indicated that some of the data submitted to IUPAC — dealing with the mysteriously stopping decay — had likely been tampered with by a collaborator to Hofmann’s lab.
Hofmann resubmitted element 112 for consideration in 2003, but was again denied due to the same problem of inconsistencies with the decay from rutherfordium to nobelium — the part of the experiment not allegedly fabricated. However, a discovery in 2004 — that rutherfordium could decay in several different ways — explained the inconsistencies, and cleared the way for 112 to be given its temporary name, ununbium, and its place on the periodic table of elements.
In July 2009, to the celebration of theoretical chemists, and consternation of chemistry students trying to memorize the periodic table, ununbium’s temporary name was dropped in favour of copernicium, signifying that element 112 is a permanent element in our universe, and in our hearts and in our minds.