Hs · Element 108 · Transition metal
One of the heaviest elements whose chemistry has been tested, one atom at a time.
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 hassium 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 hassium atoms have the same number of protons, 108, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Hs-278, has 170 neutrons and a half-life of ~19 min.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Hs-268 | 160 | — | ~0.4 sec | α |
| Hs-269 | 161 | — | 13 sec | α, SF |
| Hs-270 | 162 | — | 7.6 sec | α (50%), SF (50%) |
| Hs-273 | 165 | — | 0.51 sec | α, SF |
| Hs-278 longest-lived | 170 | — | ~19 min | SF, α |
Periodic tables list 270 for hassium: the mass number of one long-lived isotope, not an average, so mass minus atomic number gives 162, the neutron count of Hs-270.
Decay modes
~ marks a half-life whose published uncertainty is larger than the value itself.
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 hassium — too few atoms have ever existed at once.
The story
One of the heaviest elements whose chemistry has been tested, one atom at a time.
Hassium was first synthesized in 1984 by a German research team led by Peter Armbruster and Gottfried Münzenberg at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, using their advanced heavy-ion accelerator facility. The discovery involved bombarding lead-208 targets with iron-58 ions accelerated to extremely high energies, successfully creating hassium-265 through nuclear fusion reactions and detecting its characteristic decay signature. The German team used sophisticated detection systems to identify hassium atoms through their unique radioactive decay chains, confirming the synthesis of element 108 through careful analysis of nuclear events occurring over milliseconds. Initially, the element was given the systematic name "unniloctium" (meaning "one-zero-eight" in Latin) according to International Union of Pure and Applied Chemistry (IUPAC) conventions for naming undiscovered elements. The German researchers proposed the name "hassium" in honor of the German state of Hesse (Latin: Hassia), where the GSI laboratory is located, following the tradition of naming elements after places significant to their discovery. The discovery faced some controversy when Soviet scientists at the Joint Institute for Nuclear Research in Dubna claimed to have observed evidence of element 108 in earlier experiments dating back to the 1970s and 1980s. However, the Soviet claims were not considered sufficiently conclusive by the international scientific community, as their experimental evidence did not meet the rigorous standards required for confirming the discovery of new elements. IUPAC officially recognized the German team's priority in discovering hassium and approved the name "hassium" with the symbol "Hs" in 1997 after extensive review of the experimental evidence. The discovery represented a significant advancement in superheavy element research, demonstrating improved techniques for creating and detecting extremely short-lived nuclei at the limits of nuclear stability. The successful synthesis of hassium opened the door for attempts to create even heavier elements and provided crucial data for testing theories about superheavy element stability and the island of stability. This achievement required years of technological development in accelerator physics, target preparation, and ultra-sensitive detection methods for studying rare nuclear events.
Applications
Hassium, as an extremely short-lived synthetic superheavy element with half-lives measured in seconds, has no practical applications beyond fundamental scientific research into nuclear physics and the limits of atomic structure. The element serves as a critical component in studying the theoretical "island of stability," where certain superheavy nuclei are predicted to have longer half-lives and potentially useful properties. Research with hassium contributes to our understanding of nuclear shell effects and magic numbers that determine nuclear stability, providing insights crucial for advancing nuclear physics theory. The element is used to test and validate sophisticated nuclear models that predict the behavior of matter under harsh conditions, helping scientists understand how atomic nuclei behave at the limits of stability. Hassium research advances our knowledge of superheavy element chemistry, allowing scientists to study how chemical properties change as elements become increasingly heavy and relativistic effects become more pronounced. The techniques developed for detecting and analyzing hassium have contributed to improvements in particle detection technology and nuclear instrumentation used in various scientific applications. Studies of hassium provide important data for understanding stellar nucleosynthesis processes and how heavy elements are created in high-energy astrophysical environments like neutron star mergers. The element's research contributes to the development of more sophisticated theoretical models of atomic structure and nuclear physics that have broader applications in materials science and nuclear technology. While hassium itself cannot be used practically, the fundamental research it enables contributes to advancing nuclear medicine, nuclear power technology, and our understanding of the basic building blocks of matter. Future discoveries of longer-lived hassium isotopes or related superheavy elements might reveal unique properties with potential technological applications. The international collaborative efforts required for hassium research advance scientific cooperation and shared knowledge in nuclear physics research worldwide.
Hassium has no practical applications in everyday life, industry, or technology due to its extremely short half-life and the minute quantities that can be produced only in specialized particle accelerator facilities. The element is used exclusively in advanced nuclear physics research at major international scientific institutions with heavy-ion accelerator capabilities. Research laboratories study hassium to explore fundamental questions about the limits of atomic structure and the maximum number of protons that can be contained in a stable atomic nucleus. Nuclear physicists use hassium as a testing ground for theoretical models that predict the properties of superheavy elements and the proposed island of nuclear stability. The element serves as a benchmark for validating computational chemistry methods that attempt to predict the chemical behavior of superheavy elements through relativistic quantum mechanical calculations. Educational programs in nuclear physics use hassium as an example of advanced research into the fundamental nature of matter and the ongoing quest to understand atomic structure. Scientific databases and reference materials include hassium data to maintain comprehensive records of all known chemical elements and their properties. International scientific collaborations study hassium to advance global understanding of nuclear physics and share knowledge about superheavy element research. The element's study contributes to training the next generation of nuclear physicists and developing advanced experimental techniques for studying rare nuclear phenomena. While hassium cannot be used in practical applications, research into its properties advances the fundamental science underlying nuclear technologies used in medicine, energy, and materials research. The methodologies developed for hassium detection and analysis contribute to improvements in nuclear instrumentation and particle physics research techniques. The element represents a high point of current capabilities in artificial element synthesis and demonstrates the limits of what can be achieved with existing nuclear physics technology.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Hassium does not exist naturally on Earth and can only be created artificially through nuclear fusion reactions in particle accelerators, making it one of the rarest and most difficult elements to produce. The element is synthesized by bombarding heavy target nuclei with lighter projectile nuclei at extremely high energies, typically using lead-208 targets and iron-58 projectiles to create hassium-265 through nuclear fusion. Production requires sophisticated heavy-ion accelerator facilities capable of accelerating ions to precise energies while maintaining high accuracy in targeting and detection systems. Only a few atoms of hassium can be produced per hour even with the advanced accelerator technology, and these atoms decay within seconds of their creation. Hassium-269, one of the longest-lived known isotopes, has a half-life of approximately 13 seconds, while most other isotopes decay more rapidly, some within milliseconds of formation. The element's production is limited to a handful of specialized research facilities worldwide, including GSI in Germany, RIKEN in Japan, and similar institutions with appropriate accelerator capabilities. The synthetic nature of hassium means it has no geological occurrence, environmental presence, or natural reservoirs anywhere in the universe under current conditions. All hassium research must be conducted on individual atoms or very small numbers of atoms, requiring very sensitive detection equipment capable of identifying single nuclear events. The total amount of hassium ever created by humanity would be far too small to see even under the most powerful microscopes, representing perhaps a few thousand atoms produced over decades of research. Environmental concentrations of hassium are effectively zero, as the element cannot persist because of its rapid radioactive decay. Future production might increase slightly as accelerator technology advances, but hassium will remain among the rarest substances that can be created by human technology. The element exists only temporarily in the controlled environment of nuclear physics laboratories, decaying away within seconds of its creation.
Handling
Hassium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Hassium 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; hassium-269, for example, has a half-life of about 13 seconds. No weighable amount of hassium 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, which 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 (ALARA). 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
Hassium (symbol Hs) is element 108 on the periodic table, a transition metal in period 7, group 8. One of the heaviest elements whose chemistry has been tested, one atom at a time. At room temperature it is a solid, and it is radioactive.
[Rn] 5f¹⁴ 6d⁶ 7s², giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 14, 2.Hassium has no stable isotope, so it has no standard atomic weight. The figure quoted, 270, is the mass number of Hs-270, the isotope periodic tables usually list; the longest-lived one in the IAEA data is Hs-278.
Hassium has no stable isotope. Its longest-lived known isotope, Hs-278, has 170 neutrons (mass number 278 minus atomic number 108) and a half-life of ~19 min. Periodic tables list 270 for hassium, the mass number of one long-lived isotope, so mass minus atomic number gives 162, the neutron count of Hs-270.
Hassium is predicted to have a density of about 40.7 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Hassium was discovered in 1984 by GSI Darmstadt. Origin of the name: Latin Hassia, the German state of Hesse.
Hassium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Hassium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.