Lawrencium is an element with atomic symbol Lr, atomic number 103 and atomic weight of 262. It was discovered at the Lawrence Radiation Laboratory — now Lawrence Livermore National Laboratory — on the campus of the University of California at Berkeley by Albert Ghiorso, Almon E. Larsh, Robert M. Latimer, and Torbjørn Sikkeland on Valentine’s Day 1961. It was named for Ernest O. Lawrence, who invented the cyclotron. Originally designated to be represented by the atomic symbol Lw, the symbol was later changed to Lr.

Lawrencium is the last of the transuranic actinides or actinoids, as well as the last of the group to be discovered, ending a 173 year process. It all began when naturally occurring uranium was discovered by Martin Heinrich Klaproth, a German chemist, in 1789. But the development of this area lagged a bit until a spate of discoveries of the transuranic actinoids, all of which were discovered synthetically, began with Neptunium in 1940.

Lawrencium was first produced by bombarding californium with ions of boron. The small quantities of lawrencium that have up till now been created combined with lawrencium’s very short half-life makes it difficult to work with and describe. Its color, for example, is a matter of conjecture, as is its melting point.

The first isolate had a half-life of 8 seconds. Twelve isotopes have so far been synthesized — Lawrencium-252, -253, -254, -255, -256, -257, -258, -259, -260, -261, -262) and among those, the isotope with the longest half-life discovered to date is Lawrencium-262, with a half-life reported both as about three and six-tenths hours and as 216 minutes. Lawrencium-262 was first discovered in 1987 and came about in a reaction between einsteinium and neon through a nuclei transfer, and the most recent discoveries are Lawrencium-262 and -253 (m), both discovered in 2001.

Some Lawrencium isotopes have been observed to be produced by the decay of heavier elements, such as bohrium, dubnium, meitnerium, and ununtrium.