Roentgenium

Roentgenium is named after Wilhelm Röntgen, discoverer of X-rays in 1895: one of the most transformative discoveries in the history of medicine. Only a handful of atoms have been produced, each lasting less than a minute.

• Atomic Number111111 protons, 111 electrons
• Atomic Mass282.169 uOver 111× heavier than hydrogen
• State at Room TempExpected to be a Solidpredicted solid
• DensityNot measuredPredicted from periodic trends
• Melting / BoilingNot yet measuredDecays in milliseconds to hours
• Discovered1994First produced 1985s

What is Roentgenium?

Rg-282 has a half-life of approx. 100 seconds. First synthesised in 1994 at GSI. Named after Wilhelm Röntgen. Sits below gold in Group 11 and may have unusual properties due to relativistic effects.

With 111 protons, Roentgenium sits in Group 11 of the periodic table, Period 7, in the superheavy transactinide region. Its properties are predicted largely from theory and from single-atom chemistry experiments, not from bulk measurements.

Fact Roentgenium (Rg, element 111) has only ever been produced a few atoms at a time. Each atom decays within seconds. No one has ever seen, touched or measured a weighable amount of roentgenium. Everything we know about it comes from detecting individual radioactive decays and theoretical calculations.

Where you find Roentgenium

On Earth

Roentgenium does not exist naturally. It is made only artificially in nuclear physics laboratories by firing beams of one heavy nucleus at another and watching for the rare collisions that fuse them together. The main laboratories capable of producing superheavy elements are JINR in Dubna (Russia), GSI in Darmstadt (Germany), RIKEN in Japan and Lawrence Livermore National Laboratory in California.

How we use Roentgenium

Roentgenium has no practical uses. Only a handful of atoms have ever been produced, each existing for a fraction of a second to a few minutes. Research focuses on understanding nuclear structure, testing theoretical models of the atom, and searching for the predicted "island of stability", a region of superheavy nuclei that may be significantly longer-lived than those currently known.

How it was discovered

Rg-282 has a half-life of approx. 100 seconds. First synthesised in 1994 at GSI. Named after Wilhelm Röntgen. Sits below gold in Group 11 and may have unusual properties due to relativistic effects.

Deeper dive: superheavy elements and the island of stability

Nuclear physicists predict that certain combinations of protons and neutrons, "magic numbers", create particularly stable nuclei. For superheavy elements, a theoretical "island of stability" is predicted around element 114 (flerovium) or beyond, where nuclei with the right magic number of neutrons might have half-lives of years or even longer rather than milliseconds. So far, the search continues. Elements 113-118 were all officially confirmed and named in 2016, completing Period 7 of the periodic table. Whether an eighth period of elements beyond oganesson (118) can ever be made and studied remains one of the great open questions in chemistry and nuclear physics.

Superheavy elements are made by accelerating beams of lighter nuclei (often calcium-48, because of its convenient doubly-magic structure) to high energies and firing them at heavy targets (lead, bismuth, uranium, curium, californium). Very rarely, two nuclei fuse instead of bouncing apart. The fusion product is detected by its characteristic radioactive decay chain, a signature sequence of alpha decays each producing a known element, counted backwards to identify the original product.

Moving to 112 protons on the periodic table brings us to the next superheavy element.