A reprieve for Cp?

We’ve been following the story of element 112 and, like many others, have expressed surprise and/or dismay at the proposed name, copernicium, and symbol, Cp – those two letters having a place in many chemists’ hearts for the cyclopentadienyl ligand.

But wait! A letter in this week’s Nature (vol 461, p. 341) from Juris Meija, of the Canadian Institute for National Measurement Standards, suggests that there ‘could be a question mark hanging over’ the use of Cp for element 112.

And this is where it starts to get a little odd…it turns out that IUPAC rules forbid discoverers from proposing names that have previously been suggested and rejected for other elements. Although copernicium hasn’t been proposed for another element, the symbol Cp was associated with cassiopeium, a suggested name for what is now known as lutetium (which as all Asterix fans know, is named after the Latin word, Lutetia, for Paris). Extending the rule a short hop from names to symbols would therefore preclude the use of Cp.

So, rest easy, all those people concerned that they might get confused between the symbols for a widely used 5-carbon-ring ligand and a newly discovered artificial element of which a whole 3 atoms have ever existed on earth


Neil Withers (Associate Editor, Nature Chemistry)