Sg · Element 106 · Transition metal
Named for Glenn Seaborg while he was still alive — a first for the periodic table.
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 seaborgium 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 seaborgium atoms have the same number of protons, 106, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Sg-269, has 163 neutrons and a half-life of 130 sec.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Sg-263 | 157 | — | 1.0 sec | α (70%), SF (30%) |
| Sg-265 | 159 | — | 14.4 sec | SF (50%), α (50%) |
| Sg-267 | 161 | — | 84 sec | SF (83%), α (17%) |
| Sg-269 longest-lived | 163 | — | 130 sec | α, SF |
| Sg-271 | 165 | — | 96 sec | α (50%), SF (50%) |
Periodic tables list 271 for seaborgium: the mass number of one long-lived isotope, not an average, so mass minus atomic number gives 165, the neutron count of Sg-271.
Decay modes
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 247 pm — that is 0.247 nm, so about 2.02 million of them side by side would span a millimetre.
Thermal range
Neither transition has been measured for seaborgium — too few atoms have ever existed at once.
The story
Named for Glenn Seaborg while he was still alive — a first for the periodic table.
Seaborgium was discovered in June 1974 by Albert Ghiorso, J. M. Nitschke, José R. Alonso, Carol T. Alonso, M. Nurmia, G. T. Seaborg, and others at the Lawrence Berkeley National Laboratory. This discovery continued the American leadership in superheavy element synthesis during the Cold War era.
The team used Berkeley's Super Heavy Ion Linear Accelerator (SuperHILAC) to bombard californium-249 targets with oxygen-18 ions, producing seaborgium-263, whose half-life they measured as 0.9 seconds (current evaluations give about 1.0 second). This represented a major breakthrough in superheavy element synthesis techniques.
The element was named "seaborgium" after Glenn T. Seaborg (1912-1999), Nobel Prize-winning chemist who discovered ten transuranium elements and transformed nuclear chemistry. Remarkably, Seaborg was still alive when the element was named, making it the first element named after a living person.
Soviet scientists at Dubna contested the discovery priority, leading to another Cold War naming dispute. IUPAC initially rejected "seaborgium" in 1994 but reversed this decision, adopting the name in 1997; the Transfermium Working Group's 1993 report had credited Berkeley with the discovery.
The 2025 discovery of seaborgium-257 by international collaboration using the TASCA separator at GSI represents the latest advancement in seaborgium research, demonstrating continued progress in superheavy element physics with 22 observed decay events providing detailed nuclear data.
Applications
Seaborgium serves as the crucial test case for understanding Group 6 chemical behavior in superheavy elements, helping scientists determine how chromium, molybdenum, and tungsten chemical properties extend into the superheavy region under strongly relativistic conditions.
Scientists use seaborgium to investigate nuclear shell effects and stability patterns in superheavy nuclei. The recent 2025 discovery of seaborgium-257 provides new insights into fission properties and shell effects that influence superheavy element behavior.
Seaborgium enables new studies of relativistic effects in chemical bonding where electron orbital shapes and energies are dramatically altered by very high nuclear charge. These studies validate theoretical predictions about superheavy element chemistry.
Research teams employ seaborgium to study complex decay chains including alpha decay sequences, spontaneous fission, and K-isomeric states. Recent discoveries of K-isomeric states in seaborgium-259 open new avenues for exploring nuclear structure phenomena.
Seaborgium research drives innovation in ultra-sensitive analytical techniques including gas-filled separators like TASCA, advanced particle detection arrays, and sophisticated data analysis methods for identifying individual superheavy atoms.
Seaborgium applications are exclusively limited to world-leading nuclear physics facilities including GSI Helmholtz Centre in Germany, RIKEN in Japan, Berkeley Lab in the USA, and JINR in Russia. These facilities use seaborgium for advanced superheavy element research.
Research teams utilize seaborgium in advanced nuclear spectroscopy including alpha-decay energy measurements, gamma-ray detection, and nuclear lifetime studies. The 2025 discovery of seaborgium-257 demonstrates the precision achievable in modern superheavy element research.
Scientists perform important individual atom chemical studies with seaborgium, investigating oxidation states and chemical bonding using gas-phase chromatography and extraction techniques at the limits of analytical chemistry capabilities.
Seaborgium research necessitates development of modern detection systems including the TASCA separator, position-sensitive detectors, and advanced timing systems that represent a high point of nuclear physics instrumentation technology.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Seaborgium is known only from artificial synthesis in particle accelerators and has never been detected naturally on Earth or in stellar phenomena. This superheavy element has never been found anywhere in nature.
Scientists create seaborgium by bombarding californium-249 targets with oxygen-18 ions, or by bombarding lead-206/208 targets with chromium-52 ions in linear accelerators. The recent seaborgium-257 discovery used chromium-52 bombardment of lead-206 targets.
The longest-lived seaborgium isotope, 269Sg, has a half-life of only about 2 minutes (about 130 seconds) and 271Sg about 96 seconds, while the newly discovered 257Sg has a half-life of just 12.6 milliseconds. These extremely short lifetimes demonstrate the challenge of studying superheavy element properties.
Seaborgium production occurs at the level of individual atoms per experiment, with the 2025 seaborgium-257 discovery observing just 22 decay events. Worldwide annual production totals perhaps hundreds to low thousands of atoms across all research facilities.
Unlike elements formed through stellar nucleosynthesis or cosmic ray interactions, no seaborgium 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. It represents a high point of artificial element creation technology.
Handling
Seaborgium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Seaborgium is radioactive, but it is made only a few atoms at a time in heavy-ion accelerators. Its isotopes decay by alpha emission and spontaneous fission; the longest-lived, seaborgium-269, has a half-life of about 2 minutes, and seaborgium-257, first reported in 2025, shows both decay modes. No weighable amount of seaborgium 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. They are controlled by shielding and remote handling, and the waste is managed as radioactive waste under national radiation protection 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
Seaborgium (symbol Sg) is element 106 on the periodic table, a transition metal in period 7, group 6. Named for Glenn Seaborg while he was still alive — a first for the periodic table. At room temperature it is a solid, and it is radioactive.
[Rn] 5f¹⁴ 6d⁴ 7s², giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 12, 2.Seaborgium has no stable isotope, so it has no standard atomic weight. The figure quoted, 271, is the mass number of Sg-271, the isotope periodic tables usually list; the longest-lived one in the IAEA data is Sg-269.
Seaborgium has no stable isotope. Its longest-lived known isotope, Sg-269, has 163 neutrons (mass number 269 minus atomic number 106) and a half-life of 130 sec. Periodic tables list 271 for seaborgium, the mass number of one long-lived isotope, so mass minus atomic number gives 165, the neutron count of Sg-271.
Seaborgium is predicted to have a density of about 35 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Seaborgium was discovered in 1974 by Lawrence Berkeley National Laboratory. Origin of the name: Glenn T. Seaborg.
Seaborgium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Seaborgium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.