Lawrencium

Lawrencium, chemical element, symbol Lr; for physical constants see Periodic Table. Lawrencium was discovered by Albert Ghiorso and co-workers in Mar. 1961. It was incorrectly identified as Lawrencium-257, later changed to Lawrencium-258. It was prepared by bombarding a mixed-isotope californium target with boron-10 or boron-11. It has also been prepared by bombarding americium-243 with oxygen-18 ions. It is a metallic element and a member of the actinide series. Lawrencium-261 has a 40 minute half-life. That is the longest of the ten isotopes of the element now known. Lawrencium is the last member of the actinide transition series.