Lawrencium

Lawrencium is the final member of the actinide series. A Berkeley team led by Albert Ghiorso first reported it in 1961, made by bombarding californium with boron nuclei. Later work at Dubna refined the results, and both labs share the credit. It is named after Ernest Lawrence, who invented the cyclotron, the kind of particle accelerator that made so many new elements possible.

Lawrencium is made only a few atoms at a time. Its longest-lived known form, lawrencium-266, lasts about 11 hours and was identified in 2014 among the decay products of tennessine. Experiments on single atoms suggest its outermost electron is unusually loosely held, a hint of how relativity reshapes chemistry at the bottom of the table.