Copernicium

About Copernicium

Copernicium is the cleanest experimental test case we have for relativistic quantum chemistry. Sitting under mercury in group 12, it should behave like a slightly heavier Hg — but at Z=112 the inner electrons are moving fast enough that the 7s pair contracts and stabilizes dramatically, while the 6d shell expands. The prediction is that Cn doesn't really hold onto its 7s electrons as a metal would; it should sit closer to a noble gas, possibly volatile at room temperature. The 1996 GSI synthesis used a ⁷⁰Zn beam on a ²⁰⁸Pb target — a cold-fusion route that makes one atom every few weeks, with ²⁸⁵Cn living about 28 seconds before alpha-decaying to ²⁸¹Ds. The actual chemistry has only been probed on a handful of atoms via gas-phase adsorption on gold surfaces at GSI and Dubna. Those experiments showed Cn sticking to gold much more weakly than mercury does, which is exactly the relativistic-noble-gas-character signature theorists predicted. There is no use for it outside that one question.