112 Cn Copernicium 285*
Transition metal d-block Period 7 Group 12 Radioactive Synthetic

Copernicium

Cn · Element 112 · Transition metal

Predicted to be a volatile liquid — a metal that behaves almost like a noble gas.

State at 20°C Liquid~
Atomic mass 285 u
Electron configuration[Rn] 5f¹⁴ 6d¹⁰ 7s²

Structure

The copernicium atom

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.

Orbital cloud

Measured values

Property sheet

Every bar shows where copernicium sits among all 118 elements for that property.

Physical

Density 23.7 g/cm³~ 94%
Melting point 283 K~ 13%
Boiling point 340 K~ 11%
Specific heat —
Thermal conductivity —

Atomic

Atomic radius 247 pm~ 85%
Covalent radius 122 pm~
Van der Waals radius 247 pm~

Electronic

Electronegativity —
Ionisation energy 1128.9 kJ/mol~ 91%
Electron affinity —

Occurrence

Abundance in crust 0 mg/kg 0%

Identity

SymbolCn
Atomic number112
Atomic mass285 u
CategoryTransition metal
Blockd
Crystal structureunknown
Oxidation states0, +2, +4
Discovered1996
Discovered byGSI Darmstadt

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Same element, different neutrons

Isotopes of copernicium

All copernicium atoms have the same number of protons, 112, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Cn-286, has 174 neutrons and a half-life of ~11 min.

Long-lived and well-known isotopes of copernicium
ISOTOPE Neutrons Natural Abundance Half-life Decay Mode
Cn-281 169 — 0.18 sec α, SF
Cn-283 171 — 4.6 sec α (85%), SF (15%)
Cn-284 172 — 108 ms SF, α
Cn-285 173 — 33 sec α, SF
Cn-286 longest-lived 174 — ~11 min α, SF

Periodic tables list 285 for copernicium: the mass number of one long-lived isotope, not an average, so mass minus atomic number gives 173, the neutron count of Cn-285.

Decay modes

α
alpha decay
SF
spontaneous fission

~ 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

How big is a copernicium atom?

Radius 247 pm — that is 0.247 nm, so about 2.02 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Copernicium is liquid over a 57 K window, from 283 K to 340 K.

Where it sits

Position in the table

Copernicium sits in period 7, group 12. Everything in group 12 shares the same outer-electron count, which is why they behave so similarly.

Other transition metals

All transition metals

The story

What copernicium is, and how we found it

Predicted to be a volatile liquid — a metal that behaves almost like a noble gas.

The discovery of copernicium

Copernicium was first synthesized in 1996 by an international team of nuclear physicists led by Sigurd Hofmann at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, using their modern heavy-ion linear accelerator (UNILAC) and the advanced particle detection and analysis systems available at the time. The discovery involved bombarding lead-208 targets with zinc-70 ions accelerated to very high and precisely controlled energies, successfully creating copernicium-277 through nuclear fusion reactions and detecting its highly characteristic radioactive decay signature over approximately 0.24 milliseconds using sophisticated detection equipment. The German research team employed the advanced detection technology available, including advanced position-sensitive detectors, precise time-of-flight measurement systems, advanced energy analysis equipment, and complex computer-based data analysis algorithms to identify individual copernicium atoms through their unique and unmistakable decay chains and energy characteristics. The element was initially assigned the systematic placeholder name "ununbium" (meaning "one-one-two" in Latin) according to International Union of Pure and Applied Chemistry (IUPAC) systematic naming conventions established for newly discovered superheavy elements awaiting thorough scientific review and official recognition. The research team proposed the name "copernicium" to honor the Polish astronomer Nicolaus Copernicus, who fundamentally transformed our understanding of the universe by proposing the heliocentric model that placed the Sun, rather than Earth, at the center of the solar system, transforming astronomy and human understanding of our place in the cosmos. The discovery represented a major achievement in nuclear physics and accelerator technology, requiring high precision in accelerator operation, ion beam control, target preparation and positioning, timing synchronization, and detection methodology to create and positively identify atoms existing for mere fractions of a second. The successful synthesis involved many years of intensive technological development in heavy-ion accelerator physics, ultra-sensitive particle detection systems, sophisticated data acquisition and analysis techniques, and advanced statistical methods for identifying extremely rare nuclear events against complex background signals and noise. IUPAC officially approved the name "copernicium" with the chemical symbol "Cn" in 2010 after comprehensive international review of the experimental evidence, independent verification attempts by other research groups, and thorough confirmation of the discovery's scientific validity and reproducibility. The achievement demonstrated continuing rapid advancement in superheavy element research capabilities and provided essential experimental data for testing the advanced theoretical predictions about nuclear stability, atomic structure, relativistic effects, and chemical properties at the limits of the periodic table.

Applications

What copernicium is used for

Copernicium, as an extremely short-lived synthetic superheavy element with a half-life measured in seconds, has no practical applications beyond fundamental nuclear physics research and theoretical investigations into the limits of atomic structure and nuclear stability. The element serves exclusively to advance scientific understanding of superheavy nuclei and provide critical experimental data for testing sophisticated theoretical predictions about the proposed island of stability where certain superheavy elements might exhibit longer half-lives and potentially useful properties. Research with copernicium contributes significantly to validating advanced nuclear shell models and understanding how protons and neutrons organize themselves in very heavy atomic nuclei at the limits of nuclear physics. The element serves as a crucial testing ground for the most sophisticated theoretical models available that attempt to predict the chemical and physical properties of superheavy elements through complex relativistic quantum mechanical calculations and advanced computational methods. Copernicium research helps scientists understand how profound relativistic effects influence atomic behavior, electron orbital structures, and chemical properties as elements become increasingly heavy and electrons move at substantial fractions of the speed of light. The experimental techniques, instrumentation, and methodologies developed specifically for creating and detecting copernicium have significantly advanced nuclear physics technology and contributed to major improvements in particle accelerator systems, detection equipment, and data analysis methods. Studies of copernicium provide invaluable data for understanding stellar nucleosynthesis processes and how the heaviest elements in the universe are formed during the most energetic astrophysical events such as neutron star mergers, supernovae, and other high-energy cosmic phenomena. The element's research contributes substantially to training the next generation of nuclear physicists and developing important experimental methodologies for studying rare nuclear phenomena at the frontiers of current scientific and technological capability. While copernicium itself has no conceivable practical applications, the fundamental research it enables significantly advances our understanding of nuclear processes that underlie many critically important technologies in nuclear medicine, nuclear power generation, materials science, and quantum physics applications.

Copernicium has no applications whatsoever in everyday life, industry, commerce, technology, or any practical field due to the extremely short half-lives of its isotopes (about 33 seconds for copernicium-285) and the fact that only individual atoms can be produced using the advanced particle accelerator facilities available anywhere in the world. The element is used exclusively in the advanced nuclear physics research conducted at a very small number of major international laboratories equipped with the most sophisticated heavy-ion accelerators and ultra-sensitive detection systems available to modern science. Research institutions study copernicium to explore the most fundamental questions about the theoretical limits of atomic structure, nuclear stability, and the largest number of protons that can be contained within a single atomic nucleus under any conceivable conditions. Nuclear physicists use copernicium as an essential benchmark for testing and rigorously validating the advanced theoretical models and computational methods that predict the behavior, properties, and chemical characteristics of superheavy elements at the limits of the periodic table. The element serves as a critical experimental testing ground for the most sophisticated computational chemistry methods available that attempt to predict chemical properties, atomic behavior, and physical characteristics through very complex relativistic quantum mechanical calculations rather than direct experimental measurement. Educational programs in advanced nuclear physics and theoretical chemistry use copernicium as a leading example of advanced research into the most fundamental aspects of matter and the ongoing scientific quest to understand atomic structure at its theoretical and practical limits. Scientific databases, research publications, and reference materials maintain the most comprehensive records possible of copernicium's properties to ensure complete documentation of all known chemical elements, including those existing only briefly under the most specialized and controlled laboratory conditions. International scientific collaborations study copernicium to advance global understanding of superheavy element physics and foster high levels of knowledge sharing and cooperation in nuclear research at the frontiers of human scientific capability and understanding. The element's study contributes significantly to developing new experimental techniques and instrumentation for detecting and analyzing extremely rare nuclear events and ephemeral nuclear species that exist for seconds to minutes under highly controlled conditions.

Where it comes from

Natural occurrence

0 mg/kg of Earth's crust · more abundant than 0% of elements

Copernicium has never been found in nature and has only been made artificially through very complex and precisely controlled nuclear fusion reactions using the advanced and powerful particle accelerator facilities available anywhere on Earth. The element is synthesized by bombarding extremely heavy target nuclei with carefully selected lighter projectile nuclei accelerated to tremendous and precisely controlled energies, typically using zinc-70 projectiles and lead-208 targets to create copernicium-277 through meticulously controlled nuclear fusion processes requiring high precision. Production requires the most sophisticated and powerful heavy-ion accelerators in existence, capable of accelerating ions to exact energies while maintaining high accuracy in beam focusing, target positioning, timing synchronization, particle detection, and data acquisition systems operating at the limits of current technology. Even utilizing the advanced accelerator technology available to modern science and operated by the most skilled scientific teams, only individual atoms of copernicium can be produced over extended periods of intensive operation, and these atoms decay through complex radioactive processes within seconds to minutes of their creation. Copernicium-285, one of the longest-lived known isotopes, has a half-life of approximately 33 seconds, while most other known isotopes decay significantly more rapidly, some within milliseconds of their formation in the accelerator target chamber. Copernicium has been made at only a handful of laboratories, chiefly the Joint Institute for Nuclear Research in Dubna, Russia, GSI in Germany and RIKEN in Japan, institutions possessing the great technological capabilities, expertise, and resources required for superheavy element synthesis research. Copernicium has no geological occurrence on Earth or other planetary bodies and no environmental presence; whether the r-process in neutron star mergers briefly makes it is an open question. All copernicium research must be conducted on individual atoms or extremely small numbers of atoms detected through their highly characteristic and unique radioactive decay signatures, requiring the most sensitive, sophisticated, and advanced detection equipment available to modern nuclear physics research. The total quantity of copernicium ever created by humanity throughout the entire history of nuclear physics research would be far too minuscule to detect using any conventional measurement techniques, representing perhaps fewer than several dozen atoms produced over decades of intensive international research efforts involving the advanced facilities and scientific expertise available.

Handling

Safety

Copernicium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.

Copernicium 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; copernicium-285, for example, has a half-life of about 33 seconds. No weighable amount of copernicium has ever existed, so the atoms themselves cannot deliver a meaningful radiation dose to anyone. Copernicium research carries the radiological hazards typical of heavy-ion accelerator laboratories, and they 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

Copernicium: common questions

What is copernicium?

Copernicium (symbol Cn) is element 112 on the periodic table, a transition metal in period 7, group 12. Predicted to be a volatile liquid — a metal that behaves almost like a noble gas. At room temperature it is expected to be a liquid, and it is radioactive.

What is the electron configuration of copernicium?

Copernicium's ground-state electron configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s², giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 18, 2.

What are the melting and boiling points of copernicium?

No sample of copernicium has ever been condensed, so both figures are calculated rather than measured: it is predicted to melt at 283 K (9.9 °C) and boil at 340 K (66.9 °C). It will melt in a warm room or in the palm of your hand.

What is the atomic mass of copernicium?

Copernicium has no stable isotope, so it has no standard atomic weight. The figure quoted, 285, is the mass number of Cn-285, the isotope periodic tables usually list; the longest-lived one in the IAEA data is Cn-286.

How many neutrons does copernicium have?

Copernicium has no stable isotope. Its longest-lived known isotope, Cn-286, has 174 neutrons (mass number 286 minus atomic number 112) and a half-life of ~11 min. Periodic tables list 285 for copernicium, the mass number of one long-lived isotope, so mass minus atomic number gives 173, the neutron count of Cn-285.

How dense is copernicium?

Copernicium is predicted to have a density of about 23.7 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.

Who discovered copernicium, and when?

Copernicium was discovered in 1996 by GSI Darmstadt. Origin of the name: Nicolaus Copernicus.

How common is copernicium on Earth?

Copernicium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.

Is copernicium radioactive?

Yes. Copernicium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.