Copernicium – facts and properties

Position in the periodic table

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Occurrence and extraction

Copernicium is made only in accelerators. Each known isotope decays radioactively. For the longest-lived one, copernicium-285, a half-life of roughly half a minute is quoted, but the figure rests on a few atoms and is uncertain. The isotope of the discovery, copernicium-277, lasted only a fraction of a millisecond.

The proof came in 1996 at GSI in Darmstadt. The team around Sigurd Hofmann bombarded lead-208 with zinc-70 ions, again by cold fusion. The alpha decays of the atom led through darmstadtium, hassium and seaborgium to known nuclei. Copernicium-283, which became important for chemistry, is made differently: in Dubna it is formed from plutonium and calcium-48.

The name was announced on 19 February 2010, the birthday of Nicolaus Copernicus. The astronomer (1473–1543) put the Sun at the centre of the world picture. GSI had first suggested the symbol Cp. Historically, however, that was the symbol of cassiopeium, the old name for lutetium, and in chemistry Cp also stands for the cyclopentadienyl ligand. IUPAC therefore fixed Cn.

Properties and reactions

Copernicium is in period 7 and group 12, below mercury, with cadmium and zinc above. The predicted electron configuration [Rn] 5f¹⁴ 6d¹⁰ 7s² has a closed shell, as in mercury, and the atomic mass 285 u is the mass number of copernicium-285.

For the electrons this means the outer s orbital contracts because of relativistic effects and holds its two electrons very tightly. The atoms form only weak bonds with each other. That is why mercury already has such a low melting point that it is the only metal that is liquid at room temperature. In copernicium the effect should be stronger. Calculations therefore predict a melting and boiling point near room temperature. Older calculations even regarded the element as a gas, newer ones rather as an easily evaporating liquid. None of this has been measured.

The gas-phase chemistry of 2007, by a team around Robert Eichler, supports the expectation of a volatile metal. The atoms settled on gold, but less firmly than mercury atoms. That fits a metal of group 12. Whether it behaves more like a metal or more like a noble gas was debated afterwards, and the number of atoms observed stayed small. Mercury is poisonous. With copernicium, single atoms pose no danger.

Research and synthesis

Copernicium is only researched and has no application. It is interesting as the heaviest member of its group whose chemistry could be tested with single atoms, and so as a test of whether group membership still holds at the edge of the periodic table.

This is how a gas-phase experiment runs. A beam hits a target, the atoms formed are swept along by a gas stream into a long tube lined with gold detectors. The temperature falls along the tube. Where an atom sticks reveals how volatile it is, and its decay is recorded there. Since each atom is counted on its own, this is called chemistry one atom at a time. For copernicium there were too few atoms for a final verdict.

A second branch of research is nuclear physics. Copernicium isotopes lie on the paths towards still heavier nuclei. Their half-lives show how stability grows with the number of neutrons.

Quick question

What is the atomic number of copernicium (Cn)?

FAQ