Lawrencium – Lr

WRITTEN BYLester MorssAdjunct Professor, Department of Chemistry, University of Maryland, College Park, Maryland.See Article History

Alternative Titles: Lr, element 103

Lawrencium (Lr), synthetic chemical element, the 14th member of the actinoid series of the periodic table, atomic number 103. Not occurring in nature, lawrencium (probably as the isotope lawrencium-257) was first produced (1961) by chemists Albert Ghiorso, T. Sikkeland, A.E. Larsh, and R.M. Latimer at the University of California, Berkeley, by bombarding a mixture of the longest-lived isotopes of californium (atomic number 98) with boron ions (atomic number 5) accelerated in a heavy-ion linear accelerator. The element was named after American physicist Ernest O. Lawrence.

A team of Soviet scientists at the Joint Institute for Nuclear Research in Dubna discovered (1965) lawrencium-256 (26-second half-life), which the Berkeley group later used in a study with approximately 1,500 atoms to show that lawrencium behaves more like the tripositive elements in the actinoid series than like predominantly dipositive nobelium (atomic number 102). The longest-lasting isotope, lawrencium-262, has a half-life of about 3.6 hours.