Lawrencium

Lawrencium was first reported in 1961 at Berkeley by a team led by Albert Ghiorso, with a competing claim from Dubna, and the details of its discovery were only gradually resolved. It was named after Ernest Lawrence, the American physicist who invented the cyclotron. Lawrencium is an intensely radioactive synthetic metal, the last member of the actinide series, studied only atom by atom. Its longest-lived form lasts about eleven hours and it is made only a few atoms at a time; sitting just before the transactinides, it has been the subject of delicate single-atom experiments to probe where its outermost electron resides, a test of relativistic effects near the foot of the table.

Lawrence's cyclotron, first built in a rudimentary form at Berkeley in 1930 and steadily scaled up over the following decade, earned him the 1939 Nobel Prize in Physics and gave rise to two laboratories that still bear his name, Lawrence Berkeley and Lawrence Livermore, both of which went on to play central roles in creating many of the very elements, lawrencium included, that populate the bottom rows of the periodic table he never lived to see completed, since he died in 1958. His original device was small enough to fit on a tabletop, a striking contrast with the building-sized accelerators its descendants grew into within a single generation.

Lawrencium honours Ernest Orlando Lawrence, whose invention of the cyclotron, the machine that accelerates particles in a spiral to smash into target nuclei, provided the essential tool by which most of the transuranium elements were created; the Berkeley laboratory that made so many of them bears his name too. There is a fitting circularity in naming an element for the man whose machine made such elements possible. Lawrencium closes the actinide row, the second of the two detached series at the foot of the periodic table, and beyond it begin the transactinides. It has no ancient or esoteric tradition, being a synthetic element of the 1960s; its name is a tribute to the accelerator physics that turned the making of new elements from a dream into a routine, if extraordinarily difficult, craft.

Every heavy-ion accelerator used since to make elements beyond lawrencium, from Berkeley's own later machines to Germany's UNILAC at GSI and Russia's cyclotrons at Dubna, descends conceptually from Lawrence's original device, so that in a real sense his invention, rather than any single laboratory, is the common ancestor of the entire transactinide and superheavy-element enterprise. Lawrencium itself remains chemically the least studied of the actinides, since its extreme instability leaves only the barest handful of atoms available for any single experiment.