Is there a mysterious element in the periodic table that is unknown to the public?

Produced by: Science Popularization China

Author: Denovo

Producer: China Science Expo

When it comes to chemistry, most people may automatically have a series of dazzling and complex equations in their minds, or even "change color when talking about chemistry". In fact, chemistry is not that scary, and it is very close to our daily lives. From the oxygen we inhale and the carbon dioxide we exhale every day, "drinking more hot water" and soaking our feet for health, to the various accessories we wear, the various means of transportation we drive or ride, etc., there are "traces" of chemistry. It can be said that the material world is made up of chemical elements.

Since the famous Russian chemist Mendeleev proposed the periodic table in 1869, there are now 118 recorded elements, including natural and artificial elements. When scientists repeatedly review this periodic table, they also begin to think more about whether there is a mysterious element 0?

Let's start with the structure of atoms

In middle school, we learned that atoms are composed of atomic nuclei and extranuclear electrons, and are the smallest unit in chemical reactions. Among them, the atomic nucleus is composed of protons and neutrons combined by strong interaction (the unique attraction between protons and neutrons).

The number of protons is directly related to the chemical properties of the element itself, and the number of protons in the nucleus is an important sign to distinguish the types of elements. The same number of protons represents the same element, the elements with the same number of protons and neutrons are called a nuclide, and the elements with the same number of protons but different numbers of neutrons are called isotopes.

Atomic structure

(Image source: drawn by the author)

The well-known element No. 1 - Hydrogen

I believe everyone is familiar with the No. 1 element in the periodic table - hydrogen. Hydrogen is abundant in nature. Water, which is essential for human life, is composed of two elements: hydrogen and oxygen.

The most abundant of the hydrogen nuclides is 1H, which consists of only one proton and one electron. Adding a neutron will give the isotope deuterium 2H, which is the main raw material for hydrogen bombs. Since there are no neutrons in the nucleus of 1H, when the 1H atom loses its electron, the hydrogen ion is equivalent to a free proton. When a large number of hydrogen ions exist in water, the aqueous solution will become acidic. This is the process of acid ionization in water.

For example, we all know that many acids are highly corrosive. Even vinegar, a common condiment in life, can react chemically with scale, nails, etc. This is the most basic manifestation of the chemical properties of protons.

Schematic diagram of hydrogen molecule

(Source: pixabay.com)

Does element 0 really exist?

When you first hear about element 0, many people may be confused. Isn't it written in the chemistry textbook as "hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon"? Is it because my memory is confused? Don't panic! In fact, there is no element 0 in the periodic table. So, what exactly is this mysterious element 0?

The absence of element 0 in the periodic table does not mean that element 0 does not exist. Since a proton without a neutron can be an element alone, why can't a neutron without a proton be an element? Different numbers of protons represent different types of elements, so an element without protons, that is, element 0, is also called a neutron element.

As early as the beginning of the 20th century, physicist Andropov named the free neutron "element 0" and placed it at the starting position of the periodic table - just above helium, meaning the element with the least number of protons, and represented it with the symbol Nu.

However, except for a few cases of discussing nuclides or isotopes, element 0 is not included in the periodic table. Therefore, it is normal that we have never seen element 0 in the periodic table.

Neutron Star

(Image source: pixabay.com)

Aging stars contributed to the birth of element 0

Element 0 originates from the aging process of stars. When an aging star collapses, it will cause great pressure, which will press the electrons outside the hydrogen nucleus into the protons, thus forming electrically neutral neutron particles. Its structure is not stable, and the half-life of free neutrons is only about ten minutes. Under normal pressure, it will turn back into protons and release anti-electron neutrinos.

Therefore, at present, element 0 mainly exists inside extremely massive neutron stars. It is this high-pressure environment that allows the particle to exist stably. At this stage, under normal conditions, it is difficult for us to explore the chemical properties of element 0.

Four subsystems

(Image source: www.nature.com)

Although we cannot obtain neutrons under normal conditions, 20 years ago, scientific research has shown that there may be a four-neutron uncharged nuclear system. However, the instrumentation at that time had large errors, and there was great controversy in the academic community about the experimental results.

However, with the continuous progress of science and technology, it has been reported recently that a four-neutron chargeless nuclear system can exist. This is the first time that conclusive experimental evidence of the existence of a four-neutron nuclear system has been obtained. At present, research on the properties of element 0 is still in the exploratory stage. These studies will play an important role in promoting the origin of the universe, subatomic structure and other fields.

The question is, since element 0 exists, are there other new elements that are not recorded in the periodic table?

Will new elements be added to the periodic table?

The complex interactions within the nucleus are an important factor in the stability of the nucleus. According to calculations, as the atomic number continues to increase, the stability of the element first increases and then decreases, with iron, the atomic number 26, as the boundary. In other words, if all elements are arranged in a row, the farther the element is from iron, the worse its stability.

The discovery of new elements in modern times is more concentrated on superheavy elements with atomic numbers greater than 110. These superheavy elements can be artificially synthesized through atomic collisions, are radioactive and have a short lifespan. In 2010, after the synthesis of element 117, the seventh period of the periodic table was officially filled. In the following decade or so, scientists have never stopped exploring the eighth period elements.

However, due to the instability of superheavy elements, no new elements in the eighth period have been recognized by IUPAC so far. However, researchers said that through more systematic research on the interaction of microscopic particles, they believe that new synthesis methods can be proposed in the future to achieve the "stable island" of superheavy elements and construct elements in the eighth period. By that time, the opening of a new era of the periodic table is just around the corner.

References:

【1】Labarca M. An element of atomic number zero?[J]. New Journal of Chemistry, 2016, 40(11): 9002-9006.

【2】Marqués FM, Labiche M, Orr NA, et al. Detection of neutron clusters[J]. Physical Review C, 2002, 65(4): 044006.

【3】Duer M, Aumann T, Gernhäuser R, et al. Observation of a correlated free four-neutron system[J]. Nature, 2022, 606(7915): 678-682.