A "new" chemical element, want to "get into the pit" of the periodic table? It's not that easy!

Recently, researchers from the Institute of Modern Physics of the Chinese Academy of Sciences and their partners synthesized new nuclides, osmium-160 and tungsten-156, for the first time. We all know that an element is a general term for atoms of the same type with the same number of protons, while a nuclide refers to an atom with a certain number of protons and a certain number of neutrons. The discovery of this new nuclide reminds us of the past of elements.

Many people have memorized the periodic table in school, and those with a better memory can memorize it quickly, but do you know that there are many "versions" of the periodic table besides the one you memorized? Do you also know how difficult it is for a "new" chemical element to "get into the pit" of the periodic table? This article will take you into the unpopular knowledge of the periodic table.

Periodic table of elements (copyrighted image from the gallery, reprinting may cause copyright disputes)

01 Creation of the periodic table

One day in early March 1869, at a meeting of the Russian Chemical Society, Mendeleev entrusted the editor-in-chief of the "Journal of the Russian Chemical Society", Menshutkin, to read his newly written paper "The Relationship between the Properties of Elements and Atomic Weights". However, he himself left St. Petersburg and went to other provinces to continue inspecting cheese factories according to the original plan and the task entrusted to him by the Free Economic Association.

These seemingly ordinary and routine days actually announced a great scientific discovery - the birth of the periodic law of elements.

Chemical genius Mendeleev and the periodic table (copyright image of the library, reprinting may cause copyright disputes)

From a modern point of view, Mendeleev's claim that the properties of elements change periodically with their atomic weight is problematic. Although exciting phenomena such as the existence of electrons in atoms and radioactive elements in minerals were discovered later, Mendeleev was not inspired to further improve his periodic table - this is also a common phenomenon that some scientists gradually lose their creativity due to age. Later generations created many interesting periodic tables in order to study the evolution of various properties of elements.

Stoney's circular spiral periodic table (Source: Reference [2])

Huggins and Hall's cylindrical periodic table (Source: Reference [3])

For example, Stoney published a circular spiral periodic table in 1888, which can express that the relative atomic weight of an element is equal to the function of its radius and the angle of change . Another example is that the three-dimensional periodic table has been advocated by many people. The most meaningful one is probably the cylindrical periodic table proposed by Huggins and Hall in 1916. They designed two coaxial cylinders. The main group elements are located on the outer cylinder, while the sub-group elements are located on the inner cylinder to indicate that they are transition elements .

In addition to marking the group number at the bottom of the cylinder, the periodic table also uses atomic weight as a scale in the vertical direction, so that not only can the period and group number of the elements be displayed on the diagram, but the isotopes of each element can also be listed. They also listed the radioactive isotopes known at the time in the diagram. There are no less than a hundred forms of the periodic table, some of which also incorporate properties such as atomic volume, energy level, and electronegativity into the periodic table .

So much so that in 2023, when the Nobel Prize in Chemistry was awarded for the "discovery and synthesis of quantum dots", some people said that the periodic table now has a third dimension. This is probably a statement that in addition to the number of electron shells outside the nucleus and the number of outer electrons, the nanometer scale is also taken into account in the properties of elements. In fact, we can see that the periodic table has more than 3 dimensions!

Moungi G. Bawendi, Louis E. Brus and Alexei I. Ekimov, winners of the 2023 Nobel Prize in Chemistry (Source: Nobel Prize official website)

Of all these "versions" of the periodic table, the tower periodic table, proposed by Danish chemist Julius Thomsen in 1885 and optimized by Bohr in the early 1920s, has achieved good results.

02 Bohr's Periodic Table - The Battle for Element 72

Ever since Bohr proposed the theory of atomic structure in 1913, there has been an ideal to explain the periodic system of elements.

Tower-type periodic table (Source: Reference [3])

The discovery of element 72 is a famous example of the success of Bohr's periodic table theory . In 1911, French scientist Urban announced the discovery of element 72, believing it to be a rare earth element and named it "Celtium".

In May 1922, Frenchman Dauphine announced a more "reliable" result, saying that extremely weak spectral lines were found in the sample, proving that the two spectral lines came from the rare earth element "saw". Urban proudly declared in an article: " Saw has conclusively won its place among the chemical elements. "

Bohr's teacher Rutherford published a short article in Nature magazine acknowledging the results of Urban and others.

Urban and Dauphine considered element 72 to be a rare earth element and looked for it among rare earth elements. This contradicted Bohr's periodic table theory. According to Bohr's theory, element 72 should have a similar arrangement of electrons as element 40, zirconium, and therefore have similar chemical properties, and should not be considered a rare earth element .

Atomic structure of hafnium (copyright image from the library, reprinting may cause copyright disputes)

At the same time, Dauvillier's work also aroused doubts from others, some of whom said that they did not see the saw spectral line at all. Dauvillier gave a speechless answer: "Yes, it is possible, because today is not a sunny day!" Soon after, the incident ushered in a reversal. Swedish chemist Hevesy and Dutch physicist Coster discovered the real element 72 in zircon produced in Norway and Greenland and named it hafnium , thus confirming Bohr's view.

Later, Coster and others continued their hard work until they separated out element 72. As Bohr pointed out, the reason why element 72 had not been discovered was not because its content in some samples was too small, but because its properties were too similar to zirconium .

As an authoritative arbitrator, Rutherford quickly acknowledged the priority of Coster and others, and the battle for element 72 came to an end.

03 Naming new elements - competition and rules

The story of element 72 is just a microcosm of the history of element discovery and naming. Although the International Union of Pure and Applied Chemistry (IUPAC) conference held in London in 1947 initially stipulated the rules that should be followed in naming elements, sometimes such competition even rises to the national level.

In the 1960s, the United States and the Soviet Union discovered element 104 separately. Due to the unclear order of discovery, scientists from the two countries had a dispute over its name; it was not until 1997 that IUPAC named it rutherfordium.

The atomic structure of 𬬻 ( copyright image from the library, reprinting may cause copyright disputes )

Up to now, there is a relatively rigorous process for the confirmation and naming of new elements. It is roughly as follows:

First, the priority of the discovery laboratory needs to be confirmed. IUPAC and the International Union of Theoretical and Applied Physics (IUPA) will form a joint working group (JWP) to require the laboratory to provide relevant supporting documents for the discovery of the element and review the data contained in these documents.

This is a careful process. For example, when reviewing element 110, JWP considered the data of Hofmann et al. in Germany to be reassuring, and thus assessed that element 110 had been discovered by this collaboration. However, JWP commented that the data of the US laboratory did not meet the requirements.

After reviewing the priority, the JWP will inform the discoverer and the IUPAC Inorganic Chemistry Section. Within two months of receiving the JWP report, the IUPAC Inorganic Chemistry Section will invite the discoverer to propose a name and symbol for consideration. The proposal must be accompanied by a reason for the choice. The names of elements are generally taken from mythological concepts or characters (including astronomical objects), minerals or similar substances, a place or geographical area, properties of the element, scientists, etc. For example, element 105 is dubnium, with the chemical symbol Db (rhodonium), which is named after the Joint Institute for Nuclear Research in Dubna, Russia. Element 106 is seaborgium, with the chemical symbol Sg (rhodonium) , which is named after chemist Glenn Seaborg (Seaborg G.T.). Element 107 is bohrium, with the chemical symbol Bh (rhodonium) , which is named after Bohr.

The Inorganic Chemistry Division will check the suitability of the proposed names and symbols. If satisfied, it will send a provisional proposal to 15 experts, officials of other relevant committees, and the Interdepartmental Committee, and publish the information on the IUPAC website for interested individuals to view; it will also seek the opinions of IUPAP. If there is any objection, the Inorganic Chemistry Division will work with the relevant laboratories to find a way to change or replace the original name.

When these processes are completed, the final proposal for the name of the new element will be published jointly by Pure and Applied Chemistry.

From this we can see that behind the periodic table rhyme that we can recite so easily are the results of so much hardship, labor and sweat of so many scientists. It is this spirit that drives mankind to continue to move forward in exploring the world of chemistry!

References

[1] Liu Zeyuan. Commemorating the 150th Anniversary of Mendeleev's Periodic Table of Elements, Science and Culture Review, 2019, 16(1): 5-21

[2] Li Shifeng, Li Jing. Periodic System of Elements, Chengdu University of Science and Technology Press, 1994: 89-90

[3] Li Guodong, Zhou Xiaojuan, Jiang Xiaoqing, et al. The form of the periodic table, Chemical Education, 2003, 5: 43-48

[4] Georg Niels Bohr - His Life, Academics and Thoughts, Shanghai People's Publishing House, 1985: 239-243.

[5] Qin Zhi, Fan Fangli, Wu Xiaolei, et al. Synthesis and chemical properties of superheavy elements. Progress in Chemistry, 2011, 23(7): 1507-1517.

[6] Willem H. Koppenol, John Corish, Javier García-Martínez, et al. How to name new chemical elements (IUPAC Recommendations 2016), Pure Appl. Chem. 2016; 88(4): 401–405

[7] PJ KAROL, H. NAKAHARA, BW PETLEY, et al. ON THE DISCOVERY OF THE ELEMENTS 110–112 (IUPAC Technical Report), Pure Appl. Chem., 2001, Vol. 73, No. 6, pp. 959–967

Author: Huang Xiaodong , member of the China Science Writers Association , graduated from Nanjing Normal University with a degree in Applied Chemistry

Reviewer: Wang Hongpeng, Associate Researcher, China Science and Technology Museum

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.