Lawrencium Lr

Discovery

In February 1961 Albert Ghiorso, Torbjørn Sikkeland, Almon Larsh and Robert Latimer at the University of California, Berkeley, announced that they had created element 103 by bombarding a mixture of californium isotopes with boron-10 and boron-11 ions. They reported an alpha emitter with a half-life of about eight seconds and assigned it a mass number of 257.

That assignment later proved inaccurate. Between 1965 and 1967 a team at Dubna in the Soviet Union produced isotopes of element 103 through different reactions and obtained more reliable data. In 1992 the joint IUPAC–IUPAP working group recognised both Berkeley and Dubna as co-discoverers.

In 2015 researchers at the Japan Atomic Energy Agency measured the first ionisation energy of lawrencium for the first time, using just a few atoms. The value agreed closely with calculations that include relativistic effects and supported the prediction that lawrencium's outermost electron occupies a different orbital from that of its lighter relatives.

Origin of the name

The element honours Ernest Lawrence, the American physicist who invented the cyclotron, the machine that accelerates particles in a spiral and was central to the discovery of many synthetic elements. The first symbol proposed was Lw; IUPAC changed it to Lr in 1963.

Main uses

• Basic research: Lawrencium exists only a few atoms at a time and has no uses outside the laboratory.
• The shape of the periodic table: Which elements belong at the bottom of group 3 has been argued over for decades. The arrangement placing scandium, yttrium, lutetium and lawrencium in group 3 has gained wide support in recent IUPAC-related discussions and textbooks, and measurements of lawrencium's electronic structure feed directly into the discussion.
• Relativistic chemistry: In heavy atoms the inner electrons move at a sizeable fraction of the speed of light, which reshapes the orbitals. Lawrencium is a proving ground for detecting such effects experimentally.

Isotopes

Lawrencium has no stable isotopes. The longest-lived, lawrencium-266, has a half-life of about 11 hours and was identified in 2014 at the end of a decay chain starting from element 117, tennessine. Chemistry experiments usually use lawrencium-260 (about 2.7 minutes), which can be made in larger numbers, while the 2015 ionisation-energy measurement used lawrencium-256.

In everyday life

Lawrencium does not occur in nature and has no link to everyday life. It has never been produced in weighable amounts, and the pure metal has never been made. Although radioactive, it exists only as a few atoms at a time, so there is no practical exposure risk.