Lawrencium

The last of the actinides, named for Ernest Lawrence, inventor of the cyclotron.

At a glance

Symbol: Lr
Atomic number: 103
Mass number of its longest-lived isotope: [266]
Group: none; it sits in the actinide row below the table
Period: 7
Family: actinide
Electron configuration: [Rn] 5f¹⁴ 7s² 7p¹
Electronegativity: 1.30
Common ions: Lr³⁺
Isotopes: none are stable; the longest-lived last about 11 hours

On the table

Period 7, in the actinide row set below the main table. The other actinides are tinted, and every cell opens its own article.

Electrons and bonding

Radioactive, like every actinide. It gives up electrons to form positive ions.

Properties

State at 25 °C: solid
What it looks like: never made in visible amounts; expected to be a metal
Melting point: 1627 °C (predicted)
Boiling point: not known
Density: not measured

Where it is found

Not found in nature; made a few atoms at a time in particle accelerators.

Discovery and name

Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh and Robert Latimer reported it in 1961 at Berkeley after bombarding californium with boron; work at Dubna followed, and the two laboratories share the credit. It was named after Ernest Lawrence, who invented the cyclotron and founded the Berkeley laboratory.

What it is used for

Research only. Measurements on single atoms in 2015 supported the prediction that its outermost electron sits in a 7p orbital, an effect of relativity on such a heavy atom.

Handle with care

Radioactive; it has only ever existed a few atoms at a time.