Lawrencium (Lr)
Lawrencium (symbol Lr) is the chemical element with atomic number 103: an actinide, solid at 0 °C, radioactive, made artificially, with an atomic mass of 266 u. Discovered in 1961 (Albert Ghiorso et al.).
Lawrencium closes out the actinide family. It is named after Ernest Lawrence, inventor of the cyclotron, the particle accelerator that made it possible to create so many new elements. Its most stable isotope, lawrencium-266, has a half-life of about 11 hours, remarkably long for such a heavy element. Chemists still debate its exact place in the table.
Key facts
- Atomic number
- 103
- Symbol
- Lr
- French name
- Lawrencium
- Atomic mass
- 266 u
- Molar mass
- [266] g/mol
- Family
- Actinides
- Position
- period 7, d-block
- State at 0 °C
- Solid
- Melting point
- 1,626.9 °C
- Electronegativity (Pauling)
- 1.3
- First ionization energy
- 479 kJ/mol
- Electron configuration
- [Rn] 5f¹⁴ 7s² 7p¹
- Radioactive
- yes
- Discovery
- 1961, Albert Ghiorso et al.
Origin of the name
In honor of Ernest Lawrence, inventor of the cyclotron.
What does lawrencium look like?
Never observed in visible amounts; it would be a silvery metal.
Where is lawrencium found?
Absent from nature.
How is lawrencium produced?
It is made in an accelerator by bombarding a californium target with boron nuclei, or an americium target with oxygen. Lawrencium-266 has been observed as a decay product of element 117.
Top producers
- United States (Berkeley)
- Russia (Dubna)
- Japan (JAEA)
What is lawrencium used for?
- Basic research only
- Testing relativistic effects on the electrons of heavy atoms
In everyday life
- None — it exists only for moments in the lab
Role in living things
No biological role.
Hazards of lawrencium
Radioactive, but produced atom by atom: no practical danger.
Cosmic origin
- Human-made: Does not exist (or barely) in nature: synthesized in a reactor or accelerator.
History of lawrencium
In 1961, Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh and Robert Latimer at Berkeley bombarded a mix of californium isotopes with boron nuclei and detected the new element. Dubna disputed some of the results and ran its own experiments in the 1960s. In 1992, international bodies split the credit for the discovery between the two laboratories.
Did you know?
- Its symbol was originally “Lw,” replaced by “Lr” in 1963.
- In 2015, a Japanese team measured the energy needed to strip an electron from a lawrencium atom, working with just a few atoms.
- Depending on chemists' choices, it is sometimes placed below lutetium in group 3, which changes the shape of the table.
Isotopes of lawrencium
No stable isotopes; lawrencium, the last of the actinides, can only be made one atom at a time.
- lawrencium-260: radioactive, half-life 2.7 min. Long-lived enough for its chemistry to be studied atom by atom.
- lawrencium-266: radioactive, half-life 11 h. The longest-lived, observed in 2014 as a decay product of dubnium-270.
Related elements
Same family (actinides): Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U), Neptunium (Np), Plutonium (Pu), Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No).