The periodic table of the elements now officially has two new members, its heaviest ever. The new elements, 114 and 116 weigh 289 and 292 atomic mass units, respectively. By comparison, lead's atomic weight is 207.2.
These radioactive elements won't remain that heavy for long: they exist for under a second before they lose their alpha particles. Scientists once held hope that 114 would inhabit the mythical "island of stability" where ultra-heavy elements could exist for significant periods of time in large quantities, but an experiment in 2009 unfortunately found that was not the case.
We have known about the existence of these elements for over a decade (114 was discovered in 1999, 116 in 2000), so why are these only now being given official status? The committees that make the decision – the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) – are very picky about the evidence needed for something to join the periodic table. This time around they also heard arguments for elements 113, 115, and 118, which, while deemed encouraging, were ultimately decided not to fit the bill. And the recently created element 117 was not even part of the discussion.
When scientists can only create these elements for a fraction of a second, they often have to trace the products of their radioactive decay to determine what the original product was. Since space on the periodic table is the most prized real estate in science, the committees go through extensive review of the evidence before granting a new element a spot.
Elements 114 and 116 currently have placeholder names – ununquadium and ununhexium. Their Russian discoverers at Dubna Joint Institute for Nuclear Research have proposed to name 114 flerovium for Soviet nuclear physicist Georgy Flyorov and to name 116 moscovium after the region Moscow Oblast. These names seem a bit more self-congratulatory than the last (carefully chosen) element title, Copernicum, named for Copernicus, but time will tell whether they become official or not.