Lawrencium is a synthetic, highly radioactive actinide metal. It was first produced in 1961 by a team led by Albert Ghiorso at the University of California, Berkeley, and is named after Ernest O. Lawrence.
Lawrencium (Lr) is a man-made actinide with atomic number 103, located at the end of the actinide series (period 7, f-block), after nobelium (No) and before the transactinides. It is produced atom-by-atom in accelerators and studied at tracer levels.
Lr was discovered (1961) by bombarding heavy actinide targets with light ions and then rapidly separating products radiochemically. A stylized production route is:
\(^{249}\mathrm{Cf}(^{11}\mathrm{B},\,4n)\,^{256}\mathrm{Lr}\)
Other target–projectile combinations (e.g., curium or americium with oxygen/carbon beams) also yield short-lived Lr isotopes.
Commonly observed isotopes include Lr-256, Lr-257, Lr-258, and Lr-260 (half-lives from seconds to minutes). Most decay by alpha emission and sometimes spontaneous fission:
\(^{256}\mathrm{Lr} \;\to\; ^{252}\mathrm{Md} + \alpha\)
In solution, Lr(III) is the dominant state, forming hydrated cations akin to other trivalent actinides. Under strongly reducing conditions, Lr(II) can be accessed transiently for separations. The trivalent aqua ion can be represented generically as:
\(\mathrm{[Lr(H_2O)_n]^{3+}}\; (n\approx 8\text{–}9)\)
Modern spectroscopic/relativistic analyses support a ground-state configuration close to [Rn] 5f14 7s2 7p1, which helps explain some distinctive chemical behavior at the end of the actinide series.
Atoms are swept out of the target by a gas jet, then passed through rapid chromatography or on-line ion-exchange. Identification uses alpha-decay chains and characteristic energies, time correlations, and daughter products rather than bulk physical measurements.
No routine applications exist. Because only a few atoms are produced at a time and the half-lives are short, Lr is used exclusively for fundamental research in nuclear structure and late-actinide chemistry.
Yes. Lr is a radiotoxic heavy metal, but experiments use atom-to-picogram quantities. Even so, work is done with remote handling, hot cells or glove boxes, HEPA-filtered ventilation, dosimetry, and compliant radioactive-waste procedures.
At tracer scale, Lr(III) forms halides (e.g., LrCl3) and coordinates with oxygen-donor ligands (nitrates, phosphates). Redox tuning to transient Lr(II) assists in separating Lr from neighboring trivalent actinides during rapid chromatographic runs.
One illustrative production–decay sequence is:
\(^{243}\mathrm{Am}(^{18}\mathrm{O},\,5n)\,^{256}\mathrm{Lr}\)
\(^{257}\mathrm{Lr} \;\to\; ^{253}\mathrm{Md} + \alpha\)
Chains continue via successive \(\alpha\)/\(\beta\) steps toward longer-lived daughters.