How do scientists still find new elements

One of the gaps that the Russian chemist Dmitri Mendeleev had foresightedly closed in his first draft of a periodic table of the elements in 1869 was at position 43. According to its nomenclature, eka-manganese should find its place there - but first the element had to be found discover. By the 1930s, most of the loopholes in Mendeleev's sorting system had been closed. But Eka-Mangan persisted in hiding. There were already doubts that this substance would even exist on earth. Then came 1937.

The Italian physicist Emilio Segrè, who later helped build the American atom bomb, isolated a new element at the University of Palermo together with Carlo Perrier from a sample he had received from Ernest Lawrence of the University of California at Berkeley. Lawrence had stretched a molybdenum foil in his "atomic smashers" - that's what they called the particle accelerator that the atomic physicist and later Nobel laureate had constructed. The machine first accelerates atomic particles in a circular orbit to high speed and then chases them towards a target. At that time "heavy hydrogen", also called deuterium, was used as ammunition, which not only consists of a proton, like normal hydrogen, but also contains a neutron.

Segrè and Perrier boiled the sample in chemicals and came across element 43, which they later called technetium, derived from the ancient Greek word technētós, "artificial". The new element was created by the collision of molybdenum with atomic number 42 and deuterium. In some cases, the molybdenum nucleus captured a deuterium nucleus, and the molybdenum transformed into the new element, which turned out to be radioactive. This also explains why technetium had not been found in nature until then: Almost all of the reserves of this element that were present when the earth was formed have since decayed. With today's methods, traces of the element can still be detected in nature.

Information graphics

Infographic: Sara Scholz

Research: Hanno Charisius, Christian Weber

Little has changed in the way you create new elements since then. But the particle accelerators have become more powerful and the scientists are now able to bombard even short-lived artificial elements in the machines with particles. In order to produce the heaviest element to date, oganesson, which is at the bottom right with the atomic number 118 in the periodic table, physicists shot a sample of the likewise artificial element californium (atomic number 98) with calcium ions (atomic number 20). Together, the two elements bring the 118 protons of the Oganesson atom to the scales. It does not occur in nature; in the laboratory it only survives fractions of a second before it disintegrates. Large amounts of new matter do not arise in the particle spinners.

The production of new exotic elements is therefore not of commercial interest. Other elements that do not occur in nature or only in traces are of great economic interest. The radioactive americium, for example, which has so far only been found on earth in spent nuclear fuel. It is used, for example, for smoke alarms. Plutonium, nuclear fuel, fuel for rockets and building material for nuclear weapons, also only occurs in traces in nature.

After the four youngest synthetic elements Nihonium, Moscovium, Tennessine and Oganesson were officially added to the periodic table in 2016, the physicists could actually have happily switched off their machines: They had closed all the gaps in all seven series of periods. But according to calculations, there could also be an eighth period. It is possible that the elements 120 and 126 are even more durable than the youngest members of the periodic table. Some physicists consider half-lives of a few years to be possible. The properties of these hypothetical elements that have been calculated but not yet found or manufactured is still completely puzzling. The Russian nuclear physicist Yuri Oganesjan, whose team created the element 118 for the first time in 2006, even believes in another "island of stability" around the element 164.

At least the search for elements 119 and 120 has already started. Whether the periodic table will actually continue to grow remains to be seen in a few years at the earliest.