Lawrencium

Lawrencium is the last actinide element, element 103, named after Ernest Orlando Lawrence, inventor of the cyclotron particle accelerator. It was first produced in 1961 at Berkeley by bombarding californium with boron ions. Like other late actinides, it can only be made a few atoms at a time.

• Atomic Number103103 protons, 103 electrons
• Atomic Mass266.120 u103× heavier than hydrogen
• State at Room TempSolidSolid
• DensityNot measured
• Melting / Boiling1626.8°C
• Discovered1961

What is Lawrencium?

Lawrencium has 103 protons. Its most stable isotope, Lr-266, has a half-life of approx. 11 hours. Lawrencium chemistry has been studied using single atoms. It preferentially forms Lr³⁺ ions. Produced in 1961 by Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh and Robert Latimer at Berkeley.

Fact Lawrencium is element 103, symbol Lr. As an actinide, it is part of the f-block of the periodic table: one of 15 radioactive elements from actinium (89) to lawrencium (103). All actinides are radioactive; none has a stable isotope. They are produced in nuclear reactors and by decay of heavier elements, and their chemistry has been studied using only microgram or nanogram quantities.

Where you find Lawrencium

On Earth

Lawrencium does not occur in significant natural abundance. It is produced only artificially, by bombarding heavier actinide targets with neutrons or lighter ions in nuclear reactors or particle accelerators. World production is measured in nanograms or picograms, a few billion atoms at most per year.

How we use Lawrencium

At element 103, practical applications are limited by the extreme difficulty of production and the intense radioactivity. Lawrencium has 103 protons

How it was discovered

Lawrencium has 103 protons. Its most stable isotope, Lr-266, has a half-life of approx. 11 hours. Lawrencium chemistry has been studied using single atoms. It preferentially forms Lr³⁺ ions. Produced in 1961 by Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh and Robert Latimer at Berkeley.

Deeper dive: lawrencium and the actinide series

The actinides (elements 89-103) form the lower of the two rows below the main body of the periodic table. They represent the filling of the 5f electron subshell. Unlike the lanthanides (the upper row), the actinides show greater variety in their chemistry because the 5f, 6d and 7s orbitals are close in energy. The early actinides, thorium through neptunium, can show many different oxidation states (e.g. uranium from +3 to +6). The heavier actinides increasingly resemble the lanthanides in preferring the +3 state.

All actinides beyond bismuth (83) are radioactive. The lightest, thorium, protactinium and uranium, have long enough half-lives to survive from the formation of the solar system. Neptunium and beyond are almost entirely synthetic, produced in nuclear reactors or accelerators. The transuranic elements were created at remarkable facilities including Oak Ridge National Laboratory, the Berkeley Cyclotron, the GSI in Darmstadt and JINR in Dubna.

Moving to 104 protons brings us to the next element on the periodic table.