Copernicium (112)

Copernicium (originally called ununbium) is a chemical element with symbol Cn and atomic number 112. It is an extremely radioactive synthetic element that can only be created in a laboratory. The most stable known isotope, copernicium-285, has a half-life of approximately 29 seconds, but it is possible that this copernicium isotope may have a nuclear isomer with a longer half-life, 8.9 min. Copernicium was first created on 9 February, 1996 by the GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany. It is named after the astronomer Nicolaus Copernicus.

In honor of scientist and astronomer Nicolaus Copernicus (1473-1543), the discovering team around Professor Sigurd Hofmann suggested the name copernicium with the element symbol Cn (the original proposal was Cp) for the new element 112, discovered at the GSI Helmholtzzentrum für Schwerionenforschung (Center for Heavy Ion Research) in Darmstadt. It was Copernicus who discovered that the Earth orbits the Sun, thus paving the way for our modern view of the world. Thirteen years ago, element 112 was discovered by an international team of scientists at the GSI accelerator facility. A few weeks ago, the International Union of Pure and Applied Chemistry, IUPAC, officially confirmed their discovery. In around six months, IUPAC will officially endorse the new element's name. This period is set to allow the scientific community to discuss the suggested name copernicium before the IUPAC naming.

Name: Copernicium Symbol: Cn Atomic number: 112 Atomic weight: [ 285 ] Standard state: presumably a liquid at 298 K CAS Registry ID: 54084-26-3

Group in periodic table: 12 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Copernicium: historical information

Copernicium was first created on February 9, 1996, at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, by Sigurd Hofmann, Victor Ninov et al. This element was created by firing accelerated zinc-70 nuclei at a target made of lead-208 nuclei in a heavy ion accelerator. A single atom (the second was subsequently dismissed) of copernicium was produced with a mass number of 277.

In May 2000, the GSI successfully repeated the experiment to synthesize a further atom of copernicium-277. This reaction was repeated at RIKEN using the Search for a Super-Heavy Element Using a Gas-Filled Recoil Separator set-up in 2004 to synthesize two further atoms and confirm the decay data reported by the GSI team.
The IUPAC/IUPAP Joint Working Party (JWP) assessed the claim of discovery by the GSI team in 2001 and 2003. In both cases, they found that there was insufficient evidence to support their claim. This was primarily related to the contradicting decay data for the known nuclide rutherfordium-261. However, between 2001 and 2005, the GSI team studied the reaction ²⁴⁸Cm(²⁶Mg,5n)²⁶⁹Hs, and were able to confirm the decay data for hassium-269 and rutherfordium-261. It was found that the existing data on rutherfordium-261 was for an isomer, now designated rutherfordium-261m.
In May 2009, the JWP reported on the claims of discovery of element 112 again and officially recognized the GSI team as the discoverers of element 112. This decision was based on the confirmation of the decay properties of daughter nuclei as well as the confirmatory experiments at RIKEN.

Copernicium: physical properties

• Melting point: no data K
• Boiling point: 357 K
• Density of solid: 23.7 (predicted) g cm^-3
• Hexagonal close-packed crystal structure

Copernicium: orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d¹⁰.7s² (a guess based upon that of mercury)
• Shell structure:  2.8.18.32.32.18.2
• Term symbol:   ¹S₀ (a guess based upon guessed electronic structure)

Isolation

As only a few atoms of element 112 (provisionally named copernicium, Cn) have ever been made (through a nuclear reaction involving fusing a zinc atom with a lead atom) isolation of an observable quantity has never been achieved, and may well never be.

²⁰⁸Pb + ⁷⁰Zn → ²⁷⁷Cn + ¹n

This is because atoms of the element decompose through the emission of α-particles with a half life of only about 240 microseconds.