Lr · Element 103 · Actinide
The last actinide, with an electron configuration that broke the expected pattern.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where lawrencium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All lawrencium atoms have the same number of protons, 103, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Lr-266, has 163 neutrons and a half-life of ~11 hr.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Lr-260 | 157 | — | 180 sec | α, ε |
| Lr-261 | 158 | — | 39 min | SF |
| Lr-262 | 159 | — | ~4 hr | SF |
| Lr-264 | 161 | — | 4.9 hr | SF |
| Lr-266 longest-lived | 163 | — | ~11 hr | SF |
Periodic tables list 262 for lawrencium: the mass number of one long-lived isotope, not an average, so mass minus atomic number gives 159, the neutron count of Lr-262.
Decay modes
~ marks a half-life whose published uncertainty is larger than the value itself.
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
Radius 246 pm — that is 0.246 nm, so about 2.03 million of them side by side would span a millimetre.
Thermal range
Lawrencium melts at 1900 K; its boiling point has not been measured.
The story
The last actinide, with an electron configuration that broke the expected pattern.
Lawrencium was discovered in 1961 by Albert Ghiorso, Torbjørn Sikkeland, Almon E. Larsh, and Robert M. Latimer at the Lawrence Radiation Laboratory, Berkeley, using the Heavy Ion Linear Accelerator (HILAC). This discovery marked the completion of the actinide series and opened the door to superheavy element research.
The team used Berkeley's important Heavy Ion Linear Accelerator to bombard californium-252 targets with boron-10 and boron-11 ions. The resulting lawrencium-258 nuclei were detected using innovative recoil techniques and solid-state detectors, representing advanced nuclear physics technology.
The discovery employed pioneering "recoil technique" where lawrencium atoms were deposited onto metallized Mylar tape and moved past series of detectors to measure their characteristic alpha decay. This method became standard for superheavy element identification.
The element was named "lawrencium" after Ernest Orlando Lawrence (1901-1958), inventor of the cyclotron and founder of Berkeley Lab. This naming honored American contributions to nuclear physics during the intense Cold War competition in element discovery.
As the final actinide element, lawrencium's discovery marked a crucial milestone in nuclear science, providing the foundation for superheavy element research that continues today. It represented the end of one era and the beginning of exploration into uncharted nuclear territory.
Applications
Lawrencium serves as the crucial final actinide element, marking the transition point where f-orbital filling ends and d-orbital filling begins in the superheavy element region. This makes it invaluable for understanding electron configuration patterns and chemical periodicity beyond traditional elements.
Scientists use lawrencium to investigate relativistic effects in superheavy atoms, where electron velocities approach significant fractions of light speed. These studies validate quantum mechanical predictions about how chemical properties change under very high nuclear charge conditions.
Research teams employ lawrencium in pioneering single-atom chemistry experiments to determine oxidation states, ionic radii, and chemical bonding behavior. These studies help predict properties of even heavier superheavy elements and validate theoretical chemical models.
Lawrencium isotopes provide critical data for understanding nuclear magic numbers and shell effects that govern superheavy element stability. This research guides predictions about the theorized "island of stability" and optimal pathways for synthesizing elements 104 and beyond.
Studies of lawrencium drive innovation in superheavy element production methods, including hot fusion reactions, target preparation techniques, and separation chemistry that enables isolation and study of individual atoms in extremely small quantities.
Lawrencium applications remain confined to major nuclear research facilities including Berkeley Lab, GSI Helmholtz Centre, RIKEN, and the Flerov Laboratory at JINR. These institutions use lawrencium for fundamental nuclear physics and superheavy element chemistry research.
Research teams utilize lawrencium in precision nuclear measurements including alpha-decay energy determination, gamma-ray spectroscopy, and nuclear lifetime studies. These experiments provide essential data for understanding nuclear structure at the limits of atomic stability.
Scientists perform atom-at-a-time chemistry with lawrencium, studying chemical behavior using sophisticated extraction and detection techniques. These experiments represent the frontier where chemistry and nuclear physics converge.
Lawrencium research necessitates development of ultra-sensitive analytical systems including magnetic sector separators, time-of-flight detectors, and advanced data acquisition systems that push the boundaries of nuclear instrumentation technology.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Lawrencium is known only from artificial nuclear synthesis in particle accelerators. This superheavy element has never been found in nature.
Scientists create lawrencium by bombarding berkelium or californium targets with boron, carbon, or nitrogen ions in linear accelerators. The original 1961 Berkeley synthesis used a Heavy Ion Linear Accelerator (HILAC) to bombard a three-milligram target of mixed californium isotopes with boron-10 and boron-11 nuclei, producing an isotope first assigned as lawrencium-257 and later corrected to lawrencium-258.
The most stable lawrencium isotope, 266Lr, has a half-life of only 11 hours, making it impossible for any primordial lawrencium to have survived Earth's formation. Most lawrencium isotopes decay within minutes or seconds of creation.
Worldwide lawrencium production is measured in individual atoms per synthesis run, with global annual production totaling perhaps hundreds to thousands of atoms across all research facilities. Each synthesis requires rare actinide targets and enormous energy expenditure.
Unlike elements formed through stellar nucleosynthesis, cosmic ray spallation, or primordial nucleosynthesis, no lawrencium survives in nature because of its short half-lives, and whether the r-process in neutron star mergers briefly makes it is an open question. Every known lawrencium atom was made in a laboratory.
Handling
Lawrencium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Lawrencium is radioactive, but it is made only a few atoms at a time in heavy-ion accelerators. Its isotopes decay by alpha emission, electron capture and spontaneous fission; the longest-lived, lawrencium-266, has a half-life of about 11 hours. No weighable amount of lawrencium has ever existed, so the atoms themselves cannot deliver a meaningful radiation dose to anyone.
The hazards in this research come from the experiment, not the element: the accelerator beam, radioactive targets and activated equipment, and the waste these produce. Lawrencium itself decays within hours to days, so the waste comes from activated accelerator parts and targets and is managed as radioactive waste under national rules.
Staff follow the standard occupational radiation rules: annual dose limits, personal dose monitoring and keeping doses as low as reasonably achievable. Workers under 18 face much lower dose limits than adults: one tenth of the adult limits under US Nuclear Regulatory Commission rules (10 CFR 20.1207), and 1 mSv a year at US Department of Energy laboratories (10 CFR 835.207). A worker who declares a pregnancy is limited to 5 mSv to the fetus over the whole pregnancy (10 CFR 20.1208 and 835.206).
Quick answers
Lawrencium (symbol Lr) is element 103 on the periodic table, an actinide in period 7. The last actinide, with an electron configuration that broke the expected pattern. At room temperature it is expected to be a solid, and it is radioactive.
[Rn] 5f¹⁴ 7s² 7p¹, giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 8, 3.No sample of lawrencium has ever been condensed, so its melting point is calculated rather than measured: it is predicted to melt at 1900 K (1626.9 °C). Its boiling point has not been measured.
Lawrencium has no stable isotope, so it has no standard atomic weight. The figure quoted, 262, is the mass number of Lr-262, the isotope periodic tables usually list; the longest-lived one in the IAEA data is Lr-266.
Lawrencium has no stable isotope. Its longest-lived known isotope, Lr-266, has 163 neutrons (mass number 266 minus atomic number 103) and a half-life of ~11 hr. Periodic tables list 262 for lawrencium, the mass number of one long-lived isotope, so mass minus atomic number gives 159, the neutron count of Lr-262.
Lawrencium is predicted to have a density of about 15.6 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Lawrencium has a Pauling electronegativity of 1.3. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Lawrencium was discovered in 1961 by Lawrence Berkeley National Laboratory. Origin of the name: Ernest Lawrence.
Lawrencium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Lawrencium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.