How does an atom win an electron

Around the core at the speed of light

Even if the number of protons in the nucleus is decisive for the discovery of new elements - an atom always consists of electrons. They circle the atomic nucleus in different orbits. Their speed and their distance from the nucleus are mainly determined by the nuclear charge. But here is another limiting factor in how many elements there can be.

The more protons the atomic nucleus contains, the faster the electrons circle in the shell. © Probytov / iStock

Fast to the core

The basic principle is similar to the behavior of moons around a planet: the more massive the planet, the faster the moons have to orbit in order to stay in their orbit. If they are too slow, their energy will not be sufficient to withstand the gravity of the planet and they will eventually fall on it.

It is similar in the atom, except that here the charge of the nucleus is the attractive factor for the electrons: The more positively charged protons there are in the atomic nucleus, the faster the negatively charged electrons have to circle in the shell in order not to enter the nucleus fall. As a result, the electrons in gold, for example, reach more than half the speed of light.

The result: Relativistic effects occur in the atoms of heavy elements - the electrons receive more mass and energy due to their high acceleration and the electron orbitals change their shape. This gives many heavy elements special properties and is responsible for the shine of gold, for example.

The Einstein limit

But the electrons cannot become infinitely fast. According to Einstein's special theory of relativity, the speed of light forms an unbreakable limit - the cosmic speed limit, so to speak. If an atomic nucleus contains so many protons that the electrons would have to race through the atomic shell faster than light, the limit of the possible elements has also been reached.

According to current estimates, this point could be reached around elements 170 to 172. Because the electrons in these atoms can no longer become fast enough, they crash into the nucleus. There the electron merges with a proton and becomes a neutron. As a result of this process, the number of protons in the nucleus drops until the electron shell stabilizes again. The upper limit of the feasible elements could therefore be formed by this self-limiting process.

The super-heavy elements factory in Dubna opens in March 2019. © Joint Institute for Nuclear Research

Hunt for 119 and 120

But that also means: After Oganesson with the ordinal number 118, some elements could follow - theoretically. Nuclear physicists are already working on generating elements 119 and 120. At the RIKEN research center in Japan, they shoot vanadium (23) at targets made of curium (96) and hope to produce element 119.

In Dubna, a completely new accelerator facility was built especially for the hunt for these super-heavy cores. The "factory for super-heavy elements" was officially opened on March 25, 2019. You should shoot a particularly intense beam of titanium cores at targets from Berkelium and Californium to produce the elements 119 and 120.

5th April 2019

- Nadja Podbregar