Copernicium

Copernicium sits at atomic number 112, the heaviest member of Group 12 below zinc, cadmium, and mercury. Its predicted electron configuration, [Rn] 5f14 6d10 7s2, fills both the 6d and 7s subshells completely, but relativistic stabilization of the 7s electrons and spin-orbit splitting of the 6d levels are expected to push copernicium far from normal metallic behavior. Theoretical calculations suggest it may be a gas at room temperature and interact weakly with other atoms, resembling a noble gas more than a transition metal. Like all superheavy elements, copernicium exists only as individual atoms produced in accelerators, and its heaviest isotopes decay within seconds.

Copernicium is studied exclusively as a subject of fundamental research. Experiments have probed its adsorption behavior on gold surfaces inside gas-phase chromatography detectors, seeking to determine whether it behaves as a volatile metal or as a noble-gas-like species. Those measurements test relativistic electronic structure calculations at their most extreme and help establish whether the periodic table retains predictive power into the seventh period. No technological application exists or is anticipated given the element's fleeting existence.

Copernicium was first synthesized on February 9, 1996, at GSI Darmstadt by Sigurd Hofmann and colleagues, using a zinc-70 beam bombarding a lead-208 target to produce a single atom of copernicium-277. Confirmation of the discovery required additional experiments over subsequent years. IUPAC officially recognized the synthesis in 2009. The GSI team proposed the name copernicium in honor of Nicolaus Copernicus, the Polish astronomer whose heliocentric model of the solar system, published in 1543, transformed humanity's understanding of its place in the cosmos. IUPAC approved both the name and the symbol Cn in February 2010, the same year as the 537th anniversary of Copernicus's birth.

Copernicium is entirely synthetic. Its nucleus contains 112 protons and must be assembled atom by atom in a heavy-ion accelerator because no natural process on Earth or in the observable universe produces and preserves it. Even in extremely energetic astrophysical events such as neutron star mergers, any copernicium nuclei formed would decay long before reaching a detector.

No chemical compounds of copernicium have been prepared. Gas-phase experiments have studied single atoms interacting with gold detector surfaces, and the measured adsorption enthalpy suggested weaker metallic bonding than mercury, consistent with a more volatile and noble-gas-like character. Theoretical predictions indicate that copernicium fluorides such as CnF2 and CnF4 might be stable, but synthesizing even a single molecule requires atom-at-a-time chemistry that has not yet been demonstrated for this element.

• Relativistic contraction of copernicium's 7s electrons is predicted to make them so tightly bound that the element may actually be a gas at room temperature, an extraordinary departure from zinc and mercury in the same group.
• The gas-phase chromatography experiment that probed copernicium's chemical behavior used a detector containing just one atom at a time, with each event separated by days of accelerator operation.
• Copernicium is named for Nicolaus Copernicus, who never knew what an atom was; his astronomical revolution nonetheless underpins the modern scientific worldview that eventually led to the discovery of elements like this one.
• Element 112 was synthesized at GSI just two years after roentgenium (element 111), reflecting the rapid pace of superheavy element research in the mid-1990s using the same cold fusion technique.
• Some theoretical models place copernicium closer to the noble gases than to zinc on a chemical behavior scale, which would make it an honorary member of Group 18 despite its formal position in Group 12.