Copernicium (Cn), previously known as ununbium (Uub), is a chemical element with atomic number 112 (making it one of the highest-numbered and heaviest elements known to exist). Thus far, less than a hundred atoms of copernicium have ever been confirmed to exist following creation in advanced chemical experiments.
Copernicium does not occur in nature, but was created by German chemists in 1996 at the GSI Helmholtz Centre for Heavy Ion Research. These scientists used an ion accelerator to collide zinc-70 and lead-208, producing one copernicium atom with a nucleus of 112 protons and an atomic mass of 277. Subsequent experiments confirmed that copernicium-277 could be created under carefully controlled conditions, although it took several years for the International Union of Pure and Applied Chemistry to confirm the discovery and award credit to the German team. That team was then given the chance to give ununbium a permanent name, and they chose copernicium, in honour of Prussian astronomer Nicholas Copernicus. When the name was assigned in 2009, the leader of the research team, professor Sigurd Hoffman, explained that while Copernicus was better known as an astronomer than a chemist, his discoveries still "changed our world view."
Copernicium belongs to group 12 on the periodic table, below metals such as mercury. This means that it is expected that if a sufficiently large sample of copernicium could be established, it would react in chemical bonding by forming atoms with a +2 charge. For the moment, however, copernicium cannot be created easily and is highly radioactive, meaning it breaks down rather than forming long-lived samples. After the discovery of Cn-277, scientists subsequently created the heavier but stabler Cn-285, which has a half-life of about ten minutes. This means that within ten minutes, half of a given sample of copernicium will have undergone radioactive decay. When this occurs, copernicium-285 decays into darmstadtium-281, another non-natural metal which has a half-life of just over a minute. The decay process continues until eventually lighter and more stable nuclei are all that is left.
The heaviest naturally occurring element is uranium, which has 92 protons in its nucleus. The discovery of a large number of heavier metals, produced in the laboratory, has typically involved the production of more and more unstable and difficult-to-create elements. Beyond copernicium, some theories suggest that one or more elements would be stable again (known as the "island of stability"), as a result of certain hypotheses about the structure of the atomic nucleus. For the moment, however, no such stable superheavy elements have yet been created.