Measuring the Heaviest Atoms

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Science  07 Sep 2012:
Vol. 337, Issue 6099, pp. 1183-1184
DOI: 10.1126/science.1228467

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The existence of superheavy elements, those with many more protons than uranium (proton number 92), was predicted more than 40 years ago. Their increased stability against nuclear fission originates from nuclear shells that are filled with protons and neutrons, similar to the electron orbitals in an atom. For specific combinations of the number of protons and neutrons, so-called magic numbers, a more strongly bound system is formed that also has a longer half-life. The superheavy elements are predicted to populate an “island of stability” located around proton number 120 and neutron number 184. Several groups have sought to pinpoint (14) the location of this island, and along the way (5), several superheavy elements have been discovered, the latest being ununoctium with 118 protons. However, concluding whether this is the heaviest element cannot be done, and we are still far from knowing what the heaviest possible element could be. A critical point is understanding the nuclear shell effects that underlie the existence of the heaviest elements. On page 1207 of this issue, Minaya Ramirez et al. (6) shed light on such shell effects by “weighing” isotopes of the heaviest elements in an ion trap.